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The recent development of the International Medullary Thyroid Cancer Grading System (IMTCGS) provided clinicians with a tool to predict for disease outcomes after undergoing resection based on histologic features. However, its impact on the clinical management of patients is still under investigation. Utilizing the IMTCGS, we evaluated the association of grade with postoperative surveillance markers. High-grade tumors, when compared to low-grade, had a significantly more rapid calcitonin doubling time with a vast majority of high-grade patients having doubling times

Targeted inhibition of BRAF V600E achieves tumor control in a subset of advanced thyroid tumors. Nearly all tumors develop resistance, and some have been observed to subsequently undergo dedifferentiation. The molecular alterations associated with thyroid cancer dedifferentiation in the setting of BRAF inhibition are unknown. We analyzed targeted next-generation sequencing data from 639 advanced, recurrent and/or metastatic thyroid carcinomas, including 15 tumors that were treated with BRAF inhibitor drugs and had tissue sampled during or posttreatment, 8 of which had matched pretherapy samples. Pre- and posttherapy tissues from one additional patient were profiled with whole-exome sequencing and RNA expression profiling. Mutations in genes comprising the SWI/SNF chromatin remodeling complex and the PI3K–AKT–mTOR, MAPK, and JAK–STAT pathways all increased in prevalence across more dedifferentiated thyroid cancer histologies. Of 7 thyroid cancers that dedifferentiated after BRAF inhibition, 6 had mutations in these pathways. These mutations were mostly absent from matched pretreatment samples and were rarely detected in tumors that did not dedifferentiate. Additional analyses in one of the vemurafenib-treated tumors before and after anaplastic transformation revealed the emergence of an oncogenic PIK3CA mutation, activation of ERK signaling, dedifferentiation, and development of an immunosuppressive tumor microenvironment. These findings validate earlier preclinical data implicating these genetic pathways in resistance to BRAF inhibitors, and suggest that genetic alterations mediating acquired drug resistance may also promote thyroid tumor dedifferentiation.Implications:The possibility that thyroid cancer dedifferentiation may be attributed to selective pressure applied by BRAF inhibitor–targeted therapy should be investigated further.

Supplemental Figure 1. Increased clonal heterogeneity in anaplastic metastases (ATC Met 1, 5 clones Supplemental Figure 2. Copy-number alterations for the pre-vemurafenib papillary thyroid carcinoma sample Supplemental Figure 3. Differentially expressed gene analyses comparing pre-treatment PTC sample and ATC metastases in MSK-THY1. Supplemental Figure 4. Prevalence of genetic alterations linked to BRAF inhibitor resistance and/or ATC pathogenesis in primary TCGA PTCs and metastatic/recurrent PTCs, PDTCs, and ATCs sequenced by MSK-IMPACT. Supplemental Figure 5. Histology and immunohistochemical studies for MSK-THY6. Supplemental Figure 6. Mutational landscape of tumors that underwent dedifferentiation subsequent to BRAF inhibitor targeted therapy with vemurafenib or dabrafenib.

Supplemental Table 1. Genomic alterations observed in MSK-THY1 Supplemental Table 2. Cellular prevalence of single nucleotide variants in MSK-THY Supplemental Table 3. Normalized gene expression data from patient MSK-THY1 Supplemental Table 4. Mutational data for 639 thyroid tumors sequenced by MSK-IMPACT Supplemental Table 5. Mutational data for BRAFi treated thyroid cancers with post-treatment sequencing

Supplementary Figure S1. Loss of heterozygosity of Ch22q genes in poorly differentiated (PDTC) and anaplastic thyroid cancers (ATC). Supplementary Figure S2. Focal NF2-exon 4 homozygous deletion in KHM-5M anaplastic thyroid cancer cells. Supplementary Figure S3. FISH for NF2 in anaplastic thyroid cancers. Supplementary Figure S4. NF2/Merlin defects in thyroid cancer cell lines. Supplementary Figure S5. Merlin inhibits RAC1-PAK activity. Supplementary Figure S6. Merlin effects on EGFR signaling and growth of RAS mutant thyroid cancer cell lines. Supplementary Figure S7. PCR of genomic DNA from mouse thyroid tissues of the indicated genotypes with primers that distinguish wild-type from mutant Hras alleles. Supplementary Figure S8. TEAD1 is the most abundant TEAD isoform in thyroid cancer cells. Supplementary Figure S9. A) Left, Concentration-dependent growth inhibitory effects of the MEK inhibitor selumetinib (AZD6244) in RAS mutant thyroid cancer cell lines cells. Black, null/low NF2. Red, wt NF2. The IC50 of each cell line is shown in the boxed legend. Right, Western blots for merlin, pMEK and pERK in the cell lines studied. B) C643 cells expressing scrambled (pLKO.1) or shNF2 were treated with FRAX, AZD or their combination at the indicated concentrations (nM) in 1 percent of serum. Cells were counted at 6 days (*p

Targeted inhibition of BRAF V600E achieves tumor control in a subset of advanced thyroid tumors. Nearly all tumors develop resistance, and some have been observed to subsequently undergo dedifferentiation. The molecular alterations associated with thyroid cancer dedifferentiation in the setting of BRAF inhibition are unknown. We analyzed targeted next-generation sequencing data from 639 advanced, recurrent and/or metastatic thyroid carcinomas, including 15 tumors that were treated with BRAF inhibitor drugs and had tissue sampled during or posttreatment, 8 of which had matched pretherapy samples. Pre- and posttherapy tissues from one additional patient were profiled with whole-exome sequencing and RNA expression profiling. Mutations in genes comprising the SWI/SNF chromatin remodeling complex and the PI3K–AKT–mTOR, MAPK, and JAK–STAT pathways all increased in prevalence across more dedifferentiated thyroid cancer histologies. Of 7 thyroid cancers that dedifferentiated after BRAF inhibition, 6 had mutations in these pathways. These mutations were mostly absent from matched pretreatment samples and were rarely detected in tumors that did not dedifferentiate. Additional analyses in one of the vemurafenib-treated tumors before and after anaplastic transformation revealed the emergence of an oncogenic PIK3CA mutation, activation of ERK signaling, dedifferentiation, and development of an immunosuppressive tumor microenvironment. These findings validate earlier preclinical data implicating these genetic pathways in resistance to BRAF inhibitors, and suggest that genetic alterations mediating acquired drug resistance may also promote thyroid tumor dedifferentiation. Implications: The possibility that thyroid cancer dedifferentiation may be attributed to selective pressure applied by BRAF inhibitor–targeted therapy should be investigated further.

LC gene signature classifier and gene list

TMA data for ASCL1 and S100 of 173 LCs

Differentially expressed genes between AC and TC of LC1

Supplementary Figure 1: Subtype LC2 specific MEN1 loss of heterozygosity. Supplementary Figure 2: PCA on gene expression for top variable number of genes. Supplementary Figure 3: Pearson correlation on top 3000 variable genes. Supplementary Figure 4: Heatmap of top 100 variable genes. Supplementary Figure 5: PCA of top variable number of CpG sites. Supplementary Figure 6: Boxplot of gene expression of HNF1A, FOXA3 and HNF4A across three LC subtypes. Supplementary Figure 7: Low expression of HOX family members in LC2 subtype. Supplementary Figure 8: Heatmap of LCs classifier from 30 LC dataset on independent lung carcinoids cohort from Fernandez-Cuesta et al. Supplementary Figure 9: Heatmap of HNF1A, FOX3 and FEV on Fernandez-Cuesta et al gene expression dataset. Supplementary Figure 10: Key targets of ASCL1 transcription factor. Supplementary Figure 11: Clinical features of three LC subtypes for median age of diagnosis. Supplementary Table1: Tumor purity scores for 30 LC samples using gene expression profile. Supplementary Table2: Significant Pathways/Gene Ontologies for top 100 variable genes. Supplementary Table3: Global methylation CpG count under hypo (beta =0.7) methylated probes for 18 LC samples. Supplementary Table4: IHC staining results for ASCL1 and S100 biomarker in 20 LC dataset

Differentially methylated CpG probes and CpG islands

Differentially expressed genes between three LC subtypes and pathway analysis

Clinical characterization and tumor purity

Lung carcinoids (LC) are rare and slow growing primary lung neuroendocrine tumors. We performed targeted exome sequencing, mRNA sequencing, and DNA methylation array analysis on macro-dissected LCs. Recurrent mutations were enriched for genes involved in covalent histone modification/chromatin remodeling (34.5%; MEN1, ARID1A, KMT2C, and KMT2A) as well as DNA repair (17.2%) pathways. Unsupervised clustering and principle component analysis on gene expression and DNA methylation profiles showed three robust molecular subtypes (LC1, LC2, LC3) with distinct clinical features. MEN1 gene mutations were found to be exclusively enriched in the LC2 subtype. LC1 and LC3 subtypes were predominately found at peripheral and endobronchial lung, respectively. The LC3 subtype was diagnosed at a younger age than LC1 and LC2 subtypes. IHC staining of two biomarkers, ASCL1 and S100, sufficiently stratified the three subtypes. This molecular classification of LCs into three subtypes may facilitate understanding of their molecular mechanisms and improve diagnosis and clinical management.Significance:Integrative genomic analysis of lung carcinoids identifies three novel molecular subtypes with distinct clinical features and provides insight into their distinctive molecular signatures of tumorigenesis, diagnosis, and prognosis.

Mutational profile of lung carcinoid and gene ontology of mutated genes

biBackground:/i/bTumor grade is a new validated prognostic factor for medullary thyroid cancer (MTC). Calcitonin doubling time can predict MTC recurrence. We aimed to describe the association of tumor grade with calcitonin doubling and its effect on disease-specific outcomes times after resection.biMethods:/i/bA retrospective analysis of MTC patients who underwent resection at a single tertiary-care cancer center between 1986 and 2017 were evaluated. Tumors were designated as high-grade MTC if two head and neck pathologists identified mitotic index ≥5 per 2 mmsup2/sup, tumor necrosis, or a Ki67 proliferative index ≥5% within the tumor. Calcitonin doubling time was calculated using a validated calculator with at least three consecutive levels. Using Cox proportional hazards models, outcomes evaluated included locoregional relapse-free survival (LRFS), distant metastasis-free survival (DMFS), and overall survival (OS).biResults:/i/bAmong 117 patients, 95 were low grade and 22 high grade. Median follow-up was 70.2 months. High-grade patients demonstrated significantly faster calcitonin doubling times when compared with low-grade patients (8.51 ± 3.22 months vs. 38.42 ± 11.19 months;ip/i lt; 0.001). In addition, most high-grade patients (66.7%) had calcitonin doubling times less than 1 year compared with fewer low-grade patients (1.0%;ip/i lt; 0.001). High- and low-grade patients were further stratified by those who had calcitonin doubling times less than or greater than 2 years-a previously validated prognostic cutoff point. For patients with calcitonin doubling times less than 2 years, 70% were high grade, while 30% were low grade (ip/i lt; 0.001). On multivariate analysis comparing grade and calcitonin doubling times, high-grade patients had significantly worse LRFS (hazards ratio [HR] 4.77 [confidence interval; CI 1.19-8.81]), DMFS (HR 7.25 [CI 2.36-22.28]), and OS (HR 6.04 [CI 1.85-19.72];ip/i lt; 0.05 for all), while calcitonin doubling times less than 2 years had worse DMFS (HR 7.22 [CI 1.05-49.75]). High-grade patients with calcitonin doubling times less than 2 years had associated worse LRFS and OS (bothip/i lt; 0.05) compared with low-grade patients.biConclusions:/i/bThe majority of high-grade MTC patients have calcitonin doubling times less than 2years. Close monitoring should be advocated for patients assessed to have high-grade tumors as they are at risk for poor disease-specific outcomes and structural recurrence.

The genetic, biologic, and clinical heterogeneity of sarcomas poses a challenge for the identification of therapeutic targets, clinical research, and advancing patient care. Because there are > 100 sarcoma subtypes, in-depth genetic studies have focused on one or a few subtypes. Herein, we report a comparative genetic analysis of 2,138 sarcomas representing 45 pathological entities. This cohort is prospectively analyzed using targeted sequencing to characterize subtype-specific somatic alterations in targetable pathways, rates of whole genome doubling, mutational signatures, and subtype-agnostic genomic clusters. The most common alterations are in cell cycle control and TP53, receptor tyrosine kinases/PI3K/RAS, and epigenetic regulators. Subtype-specific associations include TERT amplification in intimal sarcoma and SWI/SNF alterations in uterine adenosarcoma. Tumor mutational burden, while low compared to other cancers, varies between and within subtypes. This resource will improve sarcoma models, motivate studies of subtype-specific alterations, and inform investigations of genetic factors and their correlations with treatment response.

BACKGROUND AND OBJECTIVES 18 F-fluorodeoxyglucose positron emission tomography/computed tomography (18 F-FDG-PET/CT) parameters may help distinguish malignant from benign adrenal tumors, but few have been externally validated or determined based on definitive pathological confirmation. We determined and validated a threshold for 18 F-FDG-PET/CT maximum standard uptake value (SUVmax) in patients who underwent adrenalectomy for a nonfunctional tumor. METHODS Database review identified patients with 18 F-FDG-PET/CT images available (training cohort), or only SUVmax values (validation cohort). Discriminative accuracy was assessed by area under the curve (AUC), and the optimal cutoff value estimated by maximally selected Wilcoxon rank statistics. RESULTS Of identified patients (n = 171), 86 had adrenal metastases, 20 adrenal cortical carcinoma, and 27 adrenal cortical adenoma. In the training cohort (n = 96), SUVmax was significantly higher in malignant versus benign tumors (median 8.3 vs. 3.0, p

PURPOSE Medullary thyroid carcinoma (MTC) is an aggressive neuroendocrine tumor (NET) arising from the calcitonin-producing C cells. Unlike other NETs, there is no widely accepted pathologic grading scheme. In 2020, two groups separately developed slightly different schemes (the Memorial Sloan Kettering Cancer Center and Sydney grade) on the basis of proliferative activity (mitotic index and/or Ki67 proliferative index) and tumor necrosis. Building on this work, we sought to unify and validate an internationally accepted grading scheme for MTC. PATIENTS AND METHODS Tumor tissue from 327 patients with MTC from five centers across the United States, Europe, and Australia were reviewed for mitotic activity, Ki67 proliferative index, and necrosis using uniform criteria and blinded to other clinicopathologic features. After reviewing different cutoffs, a two-tiered consensus grading system was developed. High-grade MTCs were defined as tumors with at least one of the following features: mitotic index ≥ 5 per 2 mm2, Ki67 proliferative index ≥ 5%, or tumor necrosis. RESULTS Eighty-one (24.8%) MTCs were high-grade using this scheme. In multivariate analysis, these patients demonstrated decreased overall (hazard ratio [HR] = 11.490; 95% CI, 3.118 to 32.333; P < .001), disease-specific (HR = 8.491; 95% CI, 1.461 to 49.327; P = .017), distant metastasis-free (HR = 2.489; 95% CI, 1.178 to 5.261; P = .017), and locoregional recurrence-free (HR = 2.114; 95% CI, 1.065 to 4.193; P = .032) survivals. This prognostic power was maintained in subgroup analyses of cohorts from each of the five centers. CONCLUSION This simple two-tiered international grading system is a powerful predictor of adverse outcomes in MTC. As it is based solely on morphologic assessment in conjunction with Ki67 immunohistochemistry, it brings the grading of MTCs in line with other NETs and can be readily applied in routine practice. We therefore recommend grading of MTCs on the basis of mitotic count, Ki67 proliferative index, and tumor necrosis.

The genetic, biologic, and clinical heterogeneity of sarcomas poses a challenge for the identification of therapeutic targets, clinical research, and advancing patient care. Because there are > 100 sarcoma subtypes, in-depth genetic studies have focused on one or a few subtypes. Herein, we report a comparative genetic analyses analysis of 2,138 sarcomas representing 45 pathological entities. This cohort was prospectively analyzed using targeted sequencing to characterize subtype-specific somatic alterations in targetable pathways, rates of whole genome doubling, mutational signatures, and subtype-agnostic genomic clusters. The most common alterations were in cell cycle control andTP53, receptor tyrosine kinases/PI3K/RAS, and epigenetic regulators. Subtype-specific associations includedTERTamplification in intimal sarcoma and SWI/SNF alterations in uterine adenosarcoma. Tumor mutational burden, while low compared to other cancers, varied between and within subtypes. This resource will improve sarcoma models, motivate studies of subtype-specific alterations, and inform investigations of genetic factors and their correlations with treatment response.

Lung carcinoids (LC) are rare and slow growing primary lung neuroendocrine tumors. We performed targeted exome sequencing, mRNA sequencing, and DNA methylation array analysis on macro-dissected LCs. Recurrent mutations were enriched for genes involved in covalent histone modification/chromatin remodeling (34.5%; MEN1, ARID1A, KMT2C, and KMT2A) as well as DNA repair (17.2%) pathways. Unsupervised clustering and principle component analysis on gene expression and DNA methylation profiles showed three robust molecular subtypes (LC1, LC2, LC3) with distinct clinical features. MEN1 gene mutations were found to be exclusively enriched in the LC2 subtype. LC1 and LC3 subtypes were predominately found at peripheral and endobronchial lung, respectively. The LC3 subtype was diagnosed at a younger age than LC1 and LC2 subtypes. IHC staining of two biomarkers, ASCL1 and S100, sufficiently stratified the three subtypes. This molecular classification of LCs into three subtypes may facilitate understanding of their molecular mechanisms and improve diagnosis and clinical management. Significance: Integrative genomic analysis of lung carcinoids identifies three novel molecular subtypes with distinct clinical features and provides insight into their distinctive molecular signatures of tumorigenesis, diagnosis, and prognosis.

OBJECTIVE To determine if there are differences in overall survival (OS) or event-free survival (EFS) in patients with and without concomitant extra-adrenal metastases undergoing adrenal metastasectomy. BACKGROUND There is growing interest in the use of local therapies in patients with oligometastatic disease. Previously published series have indicated that long-term survival is possible with resection. Adrenalectomy has been used to treat adrenal metastases in select patients. METHODS Patients who underwent adrenal metastasectomy from 1994 to 2015 were identified from a prospectively maintained institutional database of adrenalectomy patients, excluding adrenalectomies due to tumor extension or for palliation. Sites of disease, treatment history, and survival data were extracted from chart review. RESULTS One hundred seventy-four patients were included. Tumor histology included 68 nonsmall cell lung cancer, 34 renal cancer, 18 colorectal cancer, 11 melanoma cancer, 10 hepatocellular cancer, 8 sarcoma cancer, and 25 other cancers. The median follow-up among survivors was 5.2 (1-21) years. OS at 3 and 5 years was 50% and 40%, respectively. Patients with (n = 83) and without (n = 91) extra-adrenal metastases did not differ with respect to age, adrenal tumor size, or margin status. Median OS (3.3 years for patients with concomitant extra-adrenal metastases and 3.0 years for patients with isolated adrenal metastases; P = 0.816) and EFS (9.39 vs 9.59 months; P = 0.87) were similar. Factors negatively associated with OS included adrenal tumor size (P < 0.01), renal primary versus other (P < 0.01), and adrenal margin status (P < 0.01). CONCLUSIONS In selected patients undergoing adrenal metastasectomy, there were no significant differences in OS or EFS between patients with and without concomitant extra-adrenal metastases.

BackgroundThe ThyroSeq v2 next-generation sequencing assay (ThyroSeq) estimates the probability of malignancy in indeterminate thyroid nodules (ITN). Its diagnostic accuracy in different practice settings and patient populations is not well understood.MethodsWe analyzed 273 Bethesda III/IV ITN evaluated with ThyroSeq at 4 institutions: 2 comprehensive cancer centers (n=98 and 102), a multicenter healthcare system (n=60), and an academic medical center (n=13). The positive (PPV) and negative predictive values (NPV) of ThyroSeq, and distribution of final pathology were analyzed and compared to values predicted by Bayes Theorem.ResultsAcross 4 institutions, the PPV was 35% (22-43%), and NPV was 93% (88-100%). Predictive values correlated closely with Bayes Theorem estimates (r2=.84), although PPVs were lower than expected. RAS mutations were the most frequent molecular alteration. Among 84 RAS-mutated nodules, malignancy risk was variable (25%, range 10-37%), and distribution of benign diagnoses differed across institutions (adenoma/hyperplasia 12-85%, NIFTP 5-46%).ConclusionsIn a multi-institutional analysis, ThyroSeq PPVs were variable and lower than expected. This is attributable to differences in the prevalence of malignancy, and variability in pathologist interpretations of non-invasive tumors. It is important that clinicians understand ThyroSeq performance in their practice setting when evaluating these results.

Background: The clinical development of farnesyltransferase inhibitors (FTIs) as targeted therapy for HRAS-mutant cancers has demonstrated mixed responses dependent on cancer type. Co-occurring mutations may affect tumor response, supported by previous studies demonstrating that NF1 mutations confer resistance to HRAS inhibition by the FTI tipifarnib in thyroid cancer mouse models. We aimed to determine if PI3K pathway activating mutations altered responses to targeted therapy in HRAS-mutant cancers. Methods: Targeted sequencing data from MSK-IMPACT cohort and DFCI-GENIE (Version 9.0) database was used to investigate co-mutations amongst HRAS-mutant cancers. Fisher’s exact test was used to determine co-altered mutations found predominantly in HRAS-mutant cancers relative to respective KRAS- and NRAS-mutant cancers. ‘RASless’ (KRASlox/HRASKO/NRASKO) mouse embryonic fibroblasts (MEFs) were obtained that in the presence of 600nM tamoxifen (4OHT) resulted in a KRAS knock-out. ‘Rasless’ MEFs were transfected with HRASG13R to create a system for testing sensitivity to FTIs in the presence or absence of WT KRAS, or with concurrent PTEN loss generated by CRISPR-Cas9 technology. Results: A greater proportion of HRAS-mutant cancers had co-altered mutations (48.8%) in genes encoding effectors in the MAPK, PI3K or RTK pathways compared to KRAS- and NRAS-mutant cancers (41.4% and 38.4%, respectively; p3uM, HRASG13R = 324.7nM) and 4OHT (IC50: MEF= >3uM, HRASG13R= 0.62nM; p3uM; p Conclusions: Co-altered mutations of MAPK, PI3K or RTK effectors are found more commonly in HRAS than in KRAS or NRAS-mutant cancers. Co-alteration of PTEN preferentially associated with HRAS-mutations in NSCLC. Deletion of PTEN resulted in resistance to FTI targeted therapy in vitro. Co-altered mutations may predict sensitivity and resistance to FTIs and guide clinical trial design. Citation Format: Aradhya Nigam, Walid K. Chatila, Gnana P. Krishnamoorthy, Alan L. Ho, James A. Fagin, Nikolaus D. Schultz, Brian R. Untch. PTEN loss-of-function mutations prevalent in HRAS-mutant cancers results in resistance to targeted therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1181.

BACKGROUND: Patients with medullary thyroid carcinoma (MTC) often receive lateral lymph node dissection with total thyroidectomy when calcitonin levels are elevated, even in the absence of structural disease, but the effect of this intervention on disease specific outcomes is not known. METHODS: We retrospectively reviewed patients from 1986 to 2017 who underwent thyroidectomy with curative intent for MTC at our institution. The association of disease specific survival (DSS) and clinicopathologic features was examined using univariate and multivariate Cox regression. RESULTS: We identified 316 patients who underwent curative resection for medullary thyroid carcinoma. Overall and disease specific survival were 76% and 86% at 10-years. To investigate the effect of prophylactic ipsilateral lateral lymph node dissection, we analyzed 89 patients without known structural disease in the neck lymph nodes at the time of resection and preoperative calcitonin > 200 pg/ml, of which 45 had an ipsilateral lateral lymph node dissection (LND) and 44 did not. There were no differences in tumor size or preoperative calcitonin levels. There was no difference at 10 years in cumulative incidence of recurrence in the neck (20.9% LND vs 30.4% no LND, p=0.46), cumulative incidence of distant recurrence (18.3% vs 18.4%, p=0.97), disease specific survival (86% vs 93%, p=0.53), or overall survival at (82% vs 90%, p=0.6). CONCLUSION: Lateral neck dissection in the absence of clinical or radiologic abnormal lymph nodes is not associated with improved survival in patients with MTC.

BACKGROUND AND OBJECTIVES: (18)F-FDG-PET/CT parameters may help distinguish malignant from benign adrenal tumors, but few have been externally validated or determined based on definitive pathological confirmation. We determined and validated a threshold for (18)F-FDG-PET/CT maximum standard uptake value (SUVmax) in patients who underwent adrenalectomy for a nonfunctional tumor. METHODS: Database review identified patients with (18)F-FDG-PET/CT images available (training cohort), or only SUVmax values (validation cohort). Discriminative accuracy was assessed by area under the curve (AUC), and optimal cutoff value estimated by maximally selected Wilcoxon rank statistics. RESULTS: Of identified patients (n = 171), 86 had adrenal metastases, 20 adrenal cortical carcinoma, and 27 adrenal cortical adenoma. In the training cohort (n = 96), SUVmax was significantly higher in malignant vs. benign tumors (median 8.3 vs. 3.0, p < 0.001), with an AUC of 0.857. Tumor size did not differ. The optimal cutoff SUVmax was 4.6 (p < 0.01). In the validation cohort (n = 75), this cutoff had a sensitivity of 75%, and specificity 55%. CONCLUSIONS: (18)F-FDG-PET/CT SUVmax was associated with malignancy. Validation indicated that SUVmax ≥ 4.6 was suggestive of malignancy, while lower values did not reliably predict benign tumor.

Medullary thyroid carcinoma (MTC) is a rare nonfollicular cell-derived tumor. A robust grading system may help better stratify patients at risk for recurrence and death from disease. In total, 144 MTC between 1988 and 2018 were subjected to a detailed histopathologic evaluation. Clinical and pathologic data were correlated with disease specific survival (DSS), local recurrence free survival (LRFS) and distant metastasis free survival (DMFS). Median age was 53 years (range: 3–88). Median tumor size was 1.8 cm (range: 0.2–11). Lymph node metastases were present in 84 (58%) cases while distant metastases at presentation were found in 9 (6%) patients. Seven (5%) had ≥5 mitoses/10 HPFs. Tumor necrosis was present in 30 cases (20%) while lymphovascular invasion occurred in 41 (28%) of tumors. Extra-thyroidal extension was found in 44 (31%) and positive margins were seen in 19 (14%). There was a strong correlation between increasing tumor size and tumor necrosis (p

Emerging data suggest that not all grade 3 (G3) pancreatic neuroendocrine neoplasms (panNENs) behave the same; tumor differentiation may predict outcome.Patients with G3 panNENs treated at our institution between 1999 and 2014 were identified. Demographics, response to therapy, and overall survival were determined.Forty-five patients were identified, 16 with G3 well differentiated pancreatic neuroendocrine tumors (WD-panNETs) and 29 with poorly differentiated neuroendocrine carcinomas (PDNEC). Median overall survival in G3 WD-panNET patients was 52.2 months (95% confidence interval, 19.3-86.9 months) compared with 10.1 months (95% confidence interval, 6.9-12.4 months) in PDNEC patients (P = 0.0009). Response rate to platinum agents was 10% in G3 WD-panNETs and 37% in PDNEC. Response rate to alkylating agents was 50% in G3 WD-panNETs and 50% in PDNEC.Both G3 WD-panNETs and PDNEC responded to platinum and alkylating agents. Overall survival was significantly greater in G3 WD-panNETs compared with PDNEC. These findings challenge current classification and suggest that G3 panNENs should be classified by morphology.

PURPOSE Adrenocortical carcinomas (ACC) are rare and aggressive malignancies with limited treatment options. This study was undertaken to evaluate the immunogenicity of ACC. PATIENTS AND METHODS Patients with advanced ACC were enrolled in a phase II study to evaluate the clinical activity of pembrolizumab 200 mg every 3 weeks, without restriction on prior therapy. The primary end point was objective response rate. Efficacy was correlated with tumor programmed death-ligand 1 expression, microsatellite-high and/or mismatch repair deficient (MSI-H/MMR-D) status, and somatic and germline genomic correlates. RESULTS We enrolled 39 patients with advanced ACC and herein report after a median follow-up of 17.8 months (range, 5.4 months to 34.7 months). The objective response rate to pembrolizumab was 23% (nine patients; 95% CI, 11% to 39%), and the disease control rate was 52% (16 patients; 95% CI, 33% to 69%). The median duration of response was not reached (lower 95% CI, 4.1 months). Two of six patients with MSI-H/MMR-D tumors responded. The other seven patients with objective responses had microsatellite stable tumors. The median progression-free survival was 2.1 months (95% CI, 2.0 months to 10.7 months), and the median overall survival was 24.9 months (95% CI, 4.2 months to not reached). Thirteen percent of patients (n = 5) had treatment-related grade 3 or 4 adverse events. Tumor programmed death-ligand 1 expression and MSI-H/MMR-D status were not associated with objective response. CONCLUSION MSI-H/MMR-D tumors, for which pembrolizumab is a standard therapy, are more common in ACC than has been recognized. In advanced ACC that is microsatellite stable, pembrolizumab provided clinically meaningful and durable antitumor activity with a manageable safety profile.

Long-term outcomes after curative resection in patients with germline RET mutations and medullary thyroid cancer (MTC) are highly variable and mutation-specific oncologic outcomes are not well-described. Sixty-six patients identified from 1986 to 2017 from a single-institution cancer database were assessed for recurrence and survival using Kaplan–Meier estimates, and correlated with clinicopathologic features using log-rank or Cox proportional hazards. Median follow-up was 9.3 years (range 0.3–31.5), median tumor diameter was 1.5 cm (range 0.1–7.5), and preoperative calcitonin was known in 41 patients [median 636 (range 0–9600)]. Overall survival (OS) of the cohort was 94% at 10 years, the cumulative incidence of locoregional recurrence was 38% at 10 years, and 19/24 (79%) patients underwent repeat neck operation. The cumulative incidence of distant recurrence was 27% at 10 years. Predictors of distant recurrence were tumor size, positive lymph nodes, and pre- and postoperative carcinoembryonic antigen, but not calcitonin. M918T mutation-bearing patients had 10-year distant recurrence-free survival of 0%, compared with 83% in all other patients (p

Context Most papillary microcarcinomas (PMCs) are indolent and subclinical. However, as many as 10% can present with clinically significant nodal metastases. Objective and Design Characterization of the genomic and transcriptomic landscape of PMCs presenting with or without clinically important lymph node metastases. Subjects and Samples Formalin-fixed paraffin-embedded PMC samples from 40 patients with lateral neck nodal metastases (pN1b) and 71 patients with PMC with documented absence of nodal disease (pN0). Outcome Measures To interrogate DNA alterations in 410 genes commonly mutated in cancer and test for differential gene expression using a custom NanoString panel of 248 genes selected primarily based on their association with tumor size and nodal disease in the papillary thyroid cancer TCGA project. Results The genomic landscapes of PMC with or without pN1b were similar. Mutations in TERT promoter (3%) and TP53 (1%) were exclusive to N1b cases. Transcriptomic analysis revealed differential expression of 43 genes in PMCs with pN1b compared with pN0. A random forest machine learning–based molecular classifier developed to predict regional lymph node metastasis demonstrated a negative predictive value of 0.98 and a positive predictive value of 0.72 at a prevalence of 10% pN1b disease. Conclusions The genomic landscape of tumors with pN1b and pN0 disease was similar, whereas 43 genes selected primarily by mining the TCGA RNAseq data were differentially expressed. This bioinformatics-driven approach to the development of a custom transcriptomic assay provides a basis for a molecular classifier for pN1b risk stratification in PMC.

Purpose We assessed the usefulness of real-time molecular profiling through next-generation sequencing (NGS) in predicting the tumor biology of advanced pancreatic neuroendocrine tumors (panNETs) and in characterizing genomic evolution. Methods Patients with metastatic panNETs were recruited in the routine clinical practice setting (between May 2014 and March 2017) for prospective NGS of their tumors as well as for germline analysis using the Memorial Sloan Kettering-Integrated Mutation Profiling of Actionable Cancer Targets (MSK-IMPACT) sequencing platform. When possible, NGS was performed at multiple time points. Results NGS was performed in 96 tumor samples from 80 patients. Somatic alterations were identified in 76 of 80 patients (95%). The most commonly altered genes were MEN1 (56%), DAXX (40%), ATRX (25%), and TSC2 (25%). Alterations could be defined in pathways that included chromatin remodeling factors, histone methyltransferases, and mammalian target of rapamycin pathway genes. Somatic loss of heterozygosity was particularly prevalent (55 of 95 tested samples [58%]), and the presence of loss of heterozygosity resulted in improved overall survival (P = .06). Sequencing of pre- and post-treatment samples revealed tumor-grade progression; clonal evolution patterns were also seen (molecular resistance mechanisms and chemotherapy-associated mutagenesis). Germline genetic analysis identified clinically actionable pathogenic or likely pathogenic variants in 14 of 88 patients (16%), including mutations in high-penetrance cancer susceptibility genes ( MEN1, TSC2, and VHL). Conclusion A clinical NGS platform reveals pertubations of biologic pathways in metastatic panNETs that may inform prognosis and direct therapies. Repeat sequencing at disease progression reveals increasing tumor grade and genetic evolution, demonstrating that panNETs adopt a more aggressive behavior through time and therapies. In addition to frequent somatic mutations in MEN1 and TSC2, germline mutations in these same genes underlie susceptibility to panNETs and highlight the need to re-evaluate whether germline genetic analysis should be performed for all patients with panNETs.

Surgery remains the most important treatment modality for most types of thyroid cancer. Thyroid cancers have a remarkable spectrum of clinical behavior; well-differentiated subtypes have excellent 10-year survival rates after surgery in contrast to anaplastic thyroid cancer, which is highly lethal even with aggressive treatment. The extent of thyroidectomy and lymph node dissection should be guided by cancer subtype, preoperative workup including imaging, and disease extent. Thyroidectomy should be carried out in a stepwise fashion with the goal of removing the gland and the cancer while limiting the risk of injury to the recurrent laryngeal nerve (RLN) and parathyroid glands. The surgeon should be vigilant in identifying RLN anatomy variability, and using intraoperative nerve monitor (IONM) can be a helpful adjunct to the surgeon, particularly in complex dissections. Critical to postoperative management is the recognition and treatment of complications from thyroidectomy and lymph node dissection. Surgery for recurrent thyroid cancer can be challenging, but good surgical and oncologic outcomes can be achieved with optimal surgical planning.

Background and Objectives Patients with metastatic RCC can undergo metastasectomy to improve survival time. Our goal was to provide and compare characteristics and oncological outcomes of RCC patients who underwent complete metastasectomy at a single organ site. Methods A total of 138 RCC patients were identified as undergoing complete metastasectomy at a single organ site including adrenal, lung, liver, pancreas, or thyroid. Competing risk regression analysis was used to assess RFS and CSS adjusting for several covariates. Results In this highly selected cohort, RFS and CSS was 27% and 84% at 5 years following metastasectomy, respectively. Univariate analysis revealed that removal of multiple tumors, younger age, and a shorter interval between nephrectomy and metastasis was associated with worse RFS. Larger tumors and sarcomatoid histology at nephrectomy was associated with worse CSS. We found no evidence that metastases at the time of RCC diagnosis influenced recurrence or survival. Tumor size, number of metastases resected, and time from nephrectomy to first recurrence was significantly different, but recurrence rates were not found to be significantly different, when compared across all organ sites. Conclusions These findings inform clinical and surgical management of select RCC patients with isolated metastasis to one of several organ sites. J. Surg. Oncol. © 2016 Wiley Periodicals, Inc.

The commonly mutated genes in pancreatic neuroendocrine tumors (PanNETs) are ATRX, DAXX, and MEN1. We genotyped 64 PanNETs and found 58% carry ATRX, DAXX, and MEN1 mutations (A-D-M mutant PanNETs) and this correlates with a worse clinical outcome than tumors carrying the wild-type alleles of all three genes (A-D-M WT PanNETs). We performed RNA sequencing and DNA-methylation analysis to reveal two distinct subgroups with one consisting entirely of A-D-M mutant PanNETs. Two genes differentiating A-D-M mutant from A-D-M WT PanNETs were high ARX and low PDX1 gene expression with PDX1 promoter hyper-methylation in the A-D-M mutant PanNETs. Moreover, A-D-M mutant PanNETs had a gene expression signature related to that of alpha-cells (FDR q-value, In pancreatic neuroendocrine tumors (PanNETs) ATRX, DAXX, and MEN1 are commonly mutated (A-D-M mutant PanNETs). Here, the authors find in a cohort of PanNETS 58% are A-D-M mutant PanNETs, with a worse clinical outcome and differences in gene expression and methylation compared to A-D-M wild type cases- these gene expression differences suggest that A-D-M mutant PanNETs potentially originate from a cell type similar to alpha cells.

To analyze the natural history of small asymptomatic pancreatic neuroendocrine tumors (PanNET) and to present a matched comparison between groups who underwent either initial observation or resection. Management approach for small PanNET is uncertain. Incidentally discovered, sporadic, small (

Ch22q LOH is preferentially associated with RAS mutations in papillary and in poorly differentiated thyroid cancer (PDTC). The 22q tumor suppressor NF2, encoding merlin, is implicated in this interaction because of its frequent loss of function in human thyroid cancer cell lines. Nf2 deletion or Hras mutation is insufficient for transformation, whereas their combined disruption leads to murine PDTC with increased MAPK signaling. Merlin loss induces RAS signaling in part through inactivation of Hippo, which activates a YAP–TEAD transcriptional program. We find that the three RAS genes are themselves YAP–TEAD1 transcriptional targets, providing a novel mechanism of promotion of RAS-induced tumorigenesis. Moreover, pharmacologic disruption of YAP–TEAD with verteporfin blocks RAS transcription and signaling and inhibits cell growth. The increased MAPK output generated by NF2 loss in RAS-mutant cancers may inform therapeutic strategies, as it generates greater dependency on the MAPK pathway for viability. Significance: Intensification of mutant RAS signaling through copy-number imbalances is commonly associated with transformation. We show that NF2/merlin inactivation augments mutant RAS signaling by promoting YAP/TEAD-driven transcription of oncogenic and wild-type RAS, resulting in greater MAPK output and increased sensitivity to MEK inhibitors. Cancer Discov; 5(11); 1178–93. ©2015 AACR. This article is highlighted in the In This Issue feature, p. 1111

Of the three RAS oncoproteins, only HRAS is delocalized and inactivated by farnesyltransferase inhibitors (FTI), an approach yet to be exploited clinically. In this study, we treat mice bearing Hras-driven poorly differentiated and anaplastic thyroid cancers (Tpo-Cre/HrasG12V/p53flox/flox) with the FTI tipifarnib. Treatment caused sustained tumor regression and increased survival; however, early and late resistance was observed. Adaptive reactivation of RAS–MAPK signaling was abrogated in vitro by selective RTK (i.e., EGFR, FGFR) inhibitors, but responses were ineffective in vivo, whereas combination of tipifarnib with the MEK inhibitor AZD6244 improved outcomes. A subset of tumor-bearing mice treated with tipifarnib developed acquired resistance. Whole-exome sequencing of resistant tumors identified a Nf1 nonsense mutation and an activating mutation in Gnas at high allelic frequency, supporting the on-target effects of the drug. Cell lines modified with these genetic lesions recapitulated tipifarnib resistance in vivo. This study demonstrates the feasibility of targeting Ras membrane association in cancers in vivo and predicts combination therapies that confer additional benefit. Significance: Tipifarnib effectively inhibits oncogenic HRAS-driven tumorigenesis and abrogating adaptive signaling improves responses. NF1 and GNAS mutations drive acquired resistance to Hras inhibition, supporting the on-target effects of the drug. Cancer Res; 78(16); 4642–57. ©2018 AACR.

4112 Background: Adrenocortical carcinomas (ACC) are rare and aggressive. Treatment options are limited and marked by poor efficacy and substantial toxicity. In this phase II single-center study, the efficacy and safety of pembrolizumab was assessed in patients (pts) with advanced ACC. Methods: Enrolled pts were aged ≥18 y with advanced ACC, ECOG ≤ 1, available tumor samples for biomarker analysis. Pts received pembrolizumab 200 mg Q3W for 2 y or until disease progression, intolerable toxicity, physician/patient decision to stop treatment. Imaging was performed every 9 wks. Tumor PD-L1 positivity (modified proportion score ≥ 1% or presence of stromal interface) was evaluated. Primary endpoint was ORR (by RECIST v1.1). Secondary endpoints included DOR, PFS, OS, safety. Somatic and germline next-generation sequencing was performed. Results: 39 pts were treated. Median age 62 (range, 19-87), 28% ECOG 0, 72% received ≥ 1 therapy. In available samples to date, 7/31 (23%) PD-L1+. At time of analysis, median follow-up among survivors was 17.8 mo (range, 5.4-34.7). ORR was 23.1% (95% CI, 11.1-39.3); 0 CR, 9PR. Seven pts (17.9%) had SD as best response. Among the 9 PRs, median time to PR was 4.1 mo (range, 1.7-10.5) and median DOR was not reached (95% CI, 4.1-not reached). Three pts achieving PR have completed 2 y of treatment with ongoing response noted. Tumor PD-L1 status is currently available in 6 pts with PR, 2/6 (33%) PD-L1+. Median PFS was 2.1 mo (95% CI, 2.0-10.7). Median OS was 24.9 mo (95% CI, 4.2-not reached); 2-year OS rate was 50% (95% CI, 36-69%). In the 34 tested tumors, germline testing identified 2 PR pts with Lynch syndrome; the remaining 7 PRs were MSS. Median tumor mutation burden for all PRs was 4.1 mutations/megabase (range, 0-31.5). There was no significant relationship between somatic alterations and response to treatment. Grade 3/4 treatment-related AEs occurred in 7/39 (17.9%) pts. Two pts discontinued therapy due to AEs; both pts achieved PRs and continue to respond. All pts with PRs had LFT elevation ≥ grade 2. Conclusions: Pembrolizumab demonstrated antitumor activity and was well tolerated in advanced ACC. Durable responses were noted. Complete evaluation of tumor PD-L1 and microsatellite status will be reported at the meeting. Clinical trial information: NCT02673333.

Bilateral (or four gland) exploration remains an important component of parathyroid surgery.

Purpose Based largely on reports that predate modern reporting standards, mitotane has been considered a systemic treatment option for both hormone control and antitumor control of metastatic adrenocortical cancer (ACC), although the therapeutic window is narrow. Methods We searched electronic medical records to identify patients with metastatic ACC treated and prescribed single-agent mitotane at Memorial Sloan Kettering Cancer Center from March 15, 1989–September 18, 2015. Reference radiologists reviewed all imaging and determined efficacy according to Response Evaluation Criteria in Solid Tumors 1.1. Patient demographics, toxicities, and treatment outcomes were reviewed. Next-generation sequencing was performed in selected cases. Results Thirty-six patients were identified. The mean age was 54 and 50% had functional tumors. Grade 3 or greater toxicities were documented in 16 out of 36 patients (44%) and 17% had documented long term adrenal insufficiency. Progression of the disease as the best response occurred in 30 out of 36 patients (83%) and one patient (3%) experienced clinical progression. Three patients achieved a complete response (CR) (8%), one patient achieved a partial response (3%), and one patient (3%) had stable disease after slow disease progression prior to initiation of therapy (durable for 6 months). All responders had nonfunctional tumors. Next-generation sequencing in two of the three CR patients was performed and failed to identify any novel alterations. Conclusion In this retrospective series, mitotane had a low response rate and low tumor control rate; however, a disproportionately high complete response rate suggested it should be used in selected individuals. Adrenal insufficiency is common with mitotane use and aggressive treatment with steroid supplementation should be considered when appropriate to avoid excess toxicities. Biomarkers are desperately needed to further define this disease.

Patients with metastatic RCC can undergo metastasectomy to improve survival time. Our goal was to provide and compare characteristics and oncological outcomes of RCC patients who underwent complete metastasectomy at a single organ site.A total of 138 RCC patients were identified as undergoing complete metastasectomy at a single organ site including adrenal, lung, liver, pancreas, or thyroid. Competing risk regression analysis was used to assess RFS and CSS adjusting for several covariates.In this highly selected cohort, RFS and CSS was 27% and 84% at 5 years following metastasectomy, respectively. Univariate analysis revealed that removal of multiple tumors, younger age, and a shorter interval between nephrectomy and metastasis was associated with worse RFS. Larger tumors and sarcomatoid histology at nephrectomy was associated with worse CSS. We found no evidence that metastases at the time of RCC diagnosis influenced recurrence or survival. Tumor size, number of metastases resected, and time from nephrectomy to first recurrence was significantly different, but recurrence rates were not found to be significantly different, when compared across all organ sites.These findings inform clinical and surgical management of select RCC patients with isolated metastasis to one of several organ sites. J. Surg. Oncol. 2016;114:375-379. © 2016 Wiley Periodicals, Inc.

Pancreatic cancer comprises of several different exocrine and endocrine malignant diseases. The most common form is pancreatic adenocarcinoma, the tenth most common solid cancer in most of Western countries, which is discussed in this chapter. The lifetime risk of developing such a disease is 1.5%, with a mean age of diagnosis in the seventh decade. Unfortunately, no specific symptoms of this disease exist. Typically, patients present with unspecific abdominal discomfort, weight loss, and early satiety. More specific symptoms are painless jaundice and signs of endocrine or exocrine pancreatic insufficiency. Management of pancreatic cancer is complex and should best be performed by a multidisciplinary team. The individual components of such an approach are described in this chapter.

Praise for the previous edition: "At once a textbook, a surgical atlas, and a source of current practice guidelines...This is a high-quality, thorough and insightful resource that provides accessible and essential information...recommend[ed]." -- Doody's Review Thyroid and Parathyroid Diseases, Second Edition, has been revised and updated to reflect recent advances in the medical and surgical management of thyroid and parathyroid diseases. This new edition serves as both a comprehensive guide to patient evaluation as well as an atlas of advanced surgical techniques for managing patients needing operative intervention. Separate chapters are devoted to minimally invasive techniques and remote access/robotic thyroidectomy techniques, both of which have enjoyed increased application throughout the world. New in the second edition: * A section on state-of-the-art, evidence-based management of challenging parathyroid conditions such as multiple endocrine neoplasia and renal hyperparathyroidism * A more detailed discussion of thyroid cancer evaluation and staging * A new chapter dedicated to parathyroid cancer * Nearly 200 additional full-color illustrations This new edition is a valuable resource for all surgeons, endocrinologists, and residents seeking to expand their knowledge of thyroid and parathyroid diseases, as well as seasoned clinicians who want to improve patient care and incorporate the latest surgical advancements into their practice.

This chapter will focus on anaplastic thyroid carcinoma (ATC), thyroid lymphoma, and metastases to the thyroid gland from non-thyroid cancers. Although these entities represent three uncommon clinical scenarios, thyroid physicians should be knowledgeable on how to manage each. ATC is a highly lethal disease with survival usually measured in months. Management should be focused on diagnosis, appropriate counseling, and supportive care, and when possible, clinical trial enrollment. Thyroid lymphoma, most commonly diffuse large B-cell lymphoma (DLBCL), is not typically treated with thyroidectomy, but patients often present to the surgeon for initial management and biopsy. Lastly, metastatic disease that has spread to the thyroid gland has a number of important considerations, most notably that patients undergoing thyroid metastasectomy should be highly selected and offered resection only after multidisciplinary evaluation.

Pancreatic cancer comprises of several different exocrine and endocrine malignant diseases. The most common form is pancreatic adenocarcinoma, the tenth most common solid cancer in most of Western countries, which is discussed in this chapter. The lifetime risk of developing such a disease is 1.5%, with a mean age of diagnosis in the seventh decade. Unfortunately, no specific symptoms of this disease exist. Typically, patients present with unspecific abdominal discomfort, weight loss, and early satiety. More specific symptoms are painless jaundice and signs of endocrine or exocrine pancreatic insufficiency. Management of pancreatic cancer is complex and should best be performed by a multidisciplinary team. The individual components of such an approach are described in this chapter.

The molecular mechanisms responsible for aberrant calcium signaling in parathyroid disease are poorly understood. The loss of appropriate calcium-responsive modulation of PTH secretion observed in parathyroid disease is commonly attributed to decreased expression of the calcium-sensing receptor (CaSR), a G protein-coupled receptor. However, CaSR expression is highly variable in parathyroid adenomas, and the lack of correlation between CaSR abundance and calcium-responsive PTH kinetics indicates that mechanisms independent of CaSR expression may contribute to aberrant calcium sensing in parathyroid disease. To gain a better understanding of parathyroid tumors and the molecular determinants that drive parathyroid adenoma development, we performed gene expression profiling on a panel of 64 normal and neoplastic parathyroid tissues. The microarray data revealed high-level expression of genes known to be involved in parathyroid biology (PTH, VDR, CGA, CaSR, and GCM2). Moreover, our screen identified regulator of G protein signaling 5 (RGS5) as a candidate inhibitor of CaSR signaling. We confirmed RGS5 to be highly expressed in parathyroid adenomas relative to matched-pair normal glands. Transient expression of RGS5 in cells stably expressing CaSR resulted in dose-dependent abrogation of calcium-stimulated inositol trisphosphate production and ERK1/2 phosphorylation. Furthermore, we found that RGS5-nullizygous mice display reduced plasma PTH levels, an outcome consistent with attenuated opposition to CaSR activity. Collectively, these data suggest that RGS5 can act as a physiological regulator of calcium sensing by CaSR in the parathyroid gland. The abnormally elevated expression of RGS5 observed in parathyroid adenomas could thus represent a novel mechanism of CaSR desensitization in patients with primary hyperparathyroidism.

Pancreatic neuroendocrine tumors (PanNETs) or islet cell tumors are a rare neuroendocrine malignancy with an annual incidence of less than 1 per 100,000 per year. Current classification scheme for PanNETs include grade and stage. While well-differentiated PanNETs can be successfully treated with surgery, there are few treatments for metastatic PanNETs. A greater understanding of the cells of origin of PanNETs, tumor progression and pathway pathogenesis may guide the development of novel therapeutic options. The most commonly mutated genes in PanNETs are ATRX, DAXX, and MEN1. Little is known about the cells-of-origin for non-functional neuroendocrine tumors. Here, we genotyped 64 PanNETs for mutations in ATRX, DAXX, and MEN1 and found 37 tumors (58%) carry mutations in these three genes (A-D-M mutant PanNETs) and this correlates with a worse clinical outcome than tumors carrying the wild-type alleles of all three genes (A-D-M WT PanNETs). We performed RNA sequencing (n=33) and Illumina 450K DNA methylation (n=32) analysis on randomly selected PanNETs to reveal two distinct subgroups with one group consisting exclusively of A-D-M mutant PanNETs. Pair-wise correlation of gene expression between all PanNETs, showed A-D-M mutant PanNETs are more homogeneous as a group than A-D-M WT PanNETs. Among A-D-M mutant PanNETs, mutants with the same genotype (mutations in ATRX/DAXX/MEN1) did not show greater gene expression correlation. Two biomarkers differentiating A-D-M mutant from A-D-M WT PanNETs were high ARX gene expression and low PDX1 gene expression with PDX1 promoter hyper-methylation in the A-D-M mutant PanNETs. Moreover, A-D-M mutant PanNETs had a gene expression signature similar to that of alpha cells (pval < 0.009) of pancreatic islets including increased expression of HNF1A and its transcriptional target genes. We validated our subtype classification and A-D-M mutant panNET alpha signature using two independent PanNETs expression dataset. This gene expression profile suggests that A-D-M mutant PanNETs originate from or transdifferentiate into a distinct cell type similar to alpha cells. Citation Format: Saurabh V. Laddha, Chang S. Chan, Peter Lewis, Matthew Koletsky, Kenneth Robzyk, Edaise Da Silva, Paula J. Torres, Brian Untch, Promita Bose, Timothy Chan, David S. Klimstra, David C. Allis, Laura H. Tang. ATRX, DAXX or MEN1 mutant pancreatic neuroendocrine tumors are a distinct “alpha-cell signature” subgroup [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1799.