Search

Introduction: Clear cell renal cell carcinoma (ccRCC), the most common type of kidney cancer in adults, presents significant challenges owing to its resistance to conventional therapies. Standard treatment primarily revolves around surgical methods, particularly nephrectomy, which is critical for managing localized diseases. Despite recent advancements, the metastatic potential of ccRCC necessitates ongoing vigilance in postoperative monitoring to manage and detect disease recurrence. Recent shifts in treatment paradigms, especially with the integration of molecular patterns in ccRCC, have enabled the development of targeted therapies. Immune checkpoint and tyrosine kinase inhibitors (TKIs) have become central to managing metastatic ccRCC, offering new hope through improved survival outcomes. Recent studies have corroborated this by demonstrating the benefits of combining these therapies. Case Presentation: This report discusses a case study of a patient with high-grade ccRCC and thyroid metastases initially deemed non-resectable. The combination of immunotherapy and TKIs reduced tumor size, transforming the thyroid metastasis to a resectable state. Conclusion: This case highlights significant advancements in treatment approaches and the critical in the management of ccRCC, underscoring the necessity for continuous adaptation of clinical practices to incorporate new therapeutic developments.

Pheochromocytoma and abdominal paraganglioma (PPGL) are rare catecholamine-producing, keratin-negative, non-epithelial neuroendocrine neoplasms characterized by a unique association with syndromic diseases caused by constitutional mutations in a wide range of susceptibility genes. While PPGLs are recognized for their malignant potential, the risk of metastatic disease varies depending on several clinical, histological, and genetic factors. Accurate diagnosis and prognosis of these tumors require a multidisciplinary approach, integrating insights from various medical specialties. Pathologists play a crucial role in this complex task, as numerous morphological, immunohistochemical, and genetic findings can be linked to worse outcomes. Therefore, it is vital to stay informed about the latest advancements in PPGL pathology. This brief review provides an overview of the challenges associated with PPGLs and highlights the most recent developments in tumor prognostication.

The parathyroid cell is a vital regulator of extracellular calcium levels, operating through the secretion of parathyroid hormone (PTH). Despite its importance, the regulation of PTH secretion remains complex and not fully understood, representing a unique interplay between extracellular and intracellular calcium, and hormone secretion. One significant challenge in parathyroid research has been the difficulty in maintaining cells ex vivo for in-depth cellular investigations. To address this issue, we introduce a novel platform for parathyroid cell transplantation and noninvasive in vivo imaging using the anterior chamber of the eye as a transplantation site. We found that parathyroid adenoma tissue transplanted into the mouse eye engrafted onto the iris, became vascularized, and retained cellular composition. Transplanted animals exhibited elevated PTH levels, indicating a functional graft. With in vivo confocal microscopy, we were able to repetitively monitor parathyroid graft morphology and vascularization. In summary, there is a pressing need for new methods to study complex cellular processes in parathyroid cells. Our study provides a novel approach for noninvasive in vivo investigations that can be applied to understand parathyroid physiology and pathology under physiological and pathological conditions. This innovative strategy can deepen our knowledge on parathyroid function and disease.

Abstract The clinical significance of thyroglobulin (Tg) expression in papillary thyroid cancer (PTC) has not been systematically explored in relation to the Ki-67 index, lymph node ratio (LNR), or other conventional prognostic predictors. In this retrospective study of 327 patients with PTC, we investigated the immunohistochemical expression of Tg in both primary tumors and their matching lymph node metastases in relation to the Ki-67 index, LNR, and clinical data. Tumoral Tg immunoreactivity was inversely correlated to the Ki-67 index and tumor recurrence. The Ki-67 index was higher in lymph node metastases (mean 4%) than in the primary tumors (mean 3%). Reduced Tg expression, estimated as 0–25% Tg positive tumor cells, was more common in lymph node metastases compared to primary tumors. In addition to advanced metastatic burden (defined as N1b stage and LNR ≥ 21%), low Tg expression (0–25% positive tumor cells) in lymph node metastases had a significant prognostic impact with shorter recurrence-free survival. These findings support the potential value of histopathological assessment of Tg expression and Ki-67 index in lymph node metastases as complementary predictors to anticipate the prognosis of PTC patients better.

Abstract Background Follicular thyroid carcinomas (FTCs) rarely metastasize to regional lymph nodes, and descriptions of synchronous lateral lymph node metastases of FTC and papillary thyroid carcinoma (PTC) are lacking. Case Presentation We describe a 43-year-old female with a preoperative cytology indicating a right-sided PTC with lateral lymph node metastases. She underwent a total thyroidectomy and central and lateral lymph node dissection, and histopathology confirmed a multifocal tall cell variant PTC together with a 12 mm minimally invasive FTC in the ipsilateral lobe. While the central compartment demonstrated metastatic PTC, the lateral compartment contained PTC metastases alongside a 15 mm large follicular-patterned mass in a separate lymph node. As the cells lacked PTC associated nuclear changes, the possibility of a lateral lymph node metastasis of FTC was considered, with the possibility of ectopic thyroid tissue as a differential diagnosis. By utilizing next-generation sequencing, a Q61R NRAS mutation was pinpointed, thus proving the tissue as tumorous. The patient underwent radioiodine treatment and is currently monitored following a negative whole-body scan. Conclusions This is probably the first case report of a patient with co-existing lateral lymph node PTC and FTC metastases. Consulting previous publications, there is currently a gap of knowledge in terms of how patients with regional FTC metastases should be followed-up and treated, especially when co-occurring with spread high-risk PTC subtypes. Moreover, what guides a seemingly indolent FTC to spread via the lymphatic system remains to be defined from a molecular standpoint.

Abstract Background Thyroid cancer dedifferentiation is an unusual observation among young patients and is poorly understood, although a recent correlation to DICER1 gene mutations has been proposed. Case presentation A 28-year old patient presented with a sub-centimeter cytology-verified primary papillary thyroid carcinoma (PTC) and a synchronous lateral lymph node metastasis. Following surgery, histopathology confirmed a 9 mm oxyphilic PTC and a synchronous metastasis of poorly differentiated thyroid carcinoma (PDTC). Extensive molecular examinations of both lesions revealed wildtype DICER1 sequences, but identified a somatic ETV6-NTRK3 gene fusion and a MET germline variant (c.1076G > A, p.Arg359Gln). MET is an established oncogene known to be overexpressed in thyroid cancer, and this specific alteration was not reported as a single nucleotide polymorphism (SNP), suggestive of a mutation. Both the primary PTC and the metastatic PDTC displayed strong MET immunoreactivity. A validation cohort of 50 PTCs from young patients were analyzed using quantitative real-time PCR, revealing significantly higher MET gene expression in tumors than normal thyroid controls, a finding which was particularly pronounced in BRAF V600E mutated cases. No additional tumors apart from the index case harbored the p.Arg359Gln MET mutation. Transfecting PTC cell lines MDA-T32 and MDA-T41 with a p.Arg359Gln MET plasmid construct revealed no obvious effects on cellular migratory or invasive properties, whereas overexpression of wildtype MET stimulated invasion. Conclusions The question of whether the observed MET mutation in any way influenced the dedifferentiation of a primary PTC into a PDTC metastasis remains to be established. Moreover, our data corroborate earlier studies, indicating that MET is aberrantly expressed in PTC and may influence the invasive behavior of these tumors.

Adrenal incidentalomas are commonly detected via routine radiological procedures, and any sign of grossly invasive properties may alert the clinical team to suspect malignancy. Adreno-hepatic fusion (AHF) is a developmental disorder in which the parenchyma of the right adrenal gland is partly or wholly fused with the liver. The development of an adrenal cortical tumor in AHFs is a rare phenomenon that may mimic an invasive lesion. The index patient is a 74-year-old male with an incidental finding of a 25 mm lesion in segment VI of the liver. The lesion was deemed as fat-containing with magnetic resonance imaging (MRI) scans, and no signal was obtained on fluorodeoxyglucose-positron emission tomography (FDG-PET). A core needle biopsy was taken, and histology displayed adrenal cortical tumor lacking pleomorphism, mitoses and necrosis intermingled with hepatocytes. The favored diagnosis was adrenal cortical adenoma (ACA) arising in an AHF. Surgical resection was subsequently performed, thus verifying the diagnosis. A review of the current literature identified 10 cases with ACA development in AHF, predominantly detected as incidental masses in older female patients, and always positive for markers of adrenal differentiation when assessed. We conclude that radiological evidence of an adrenal tumor adherent to the liver capsule should not automatically imply adrenal cortical carcinoma, especially if the tumor is small and FDG-PET negative. Although exceedingly rare, adenoma formation in a pre-existing AHF should constitute a differential diagnosis in this specific clinical setting. Moreover, adrenal cortical immunohistochemical markers seem to correctly identify the tissue origin in these rare malformations.

Parathyroid adenoma is a tumor composed of increased parenchymal tissue, often built-up by chief cells, transitional cells or oncocytic cells arranged in acinar or solid formations. Occasionally, rare histological patterns are reported, including cystic or trabecular arrangements. We present a 47 year-old male patient with primary hyperparathyroidism who underwent focused parathyroidectomy for a right inferior adenoma. Surgery was uneventful, but histologically, normal parathyroid tissue adjacent to a tumorous structure displaying a cystic growth pattern was detected. The cells lining the cyst walls appeared cylindrical and pseudo-stratified, vaguely reminiscent of a respiratory type of epithelium usually associated to branchial cleft cysts or thyroglossal cyst remnants, albeit with a tumorous appearance. The respiratory-like epithelium stained positive for parathyroid markers PTH and GATA3, thereby confirming them as parathyroid-derived. The patient was cured from surgery as he displayed normal calcium and PTH levels postoperatively, and is currently alive and well without signs of relapse 4 years after surgery. This is to our knowledge the first report of a parathyroid tumor displaying a respiratory-like epithelium. Experimentally, canine parathyroid glands can develop ciliated respiratory epithelium in response to inhalation of ozone. Our patient is a construction worker with a hypothetically increased risk of continuous ozone exposure. Although this association remains purely speculative, future investigations of this tumor phenotype could perhaps yield novel insights regarding the frequency of this histological variant, potential clinical associations, and clues regarding influencing factors.

Telomere maintenance is a critical requirement for enabling replicative immortality and tumour development. Here, telomerase expression and activity, telomere length (TL) and potential regulatory factors that can underlie telomerase machinery alterations in small intestinal neuroendocrine tumours (SI-NETs) were analyzed. Telomerase activity assessed by TRAP assay was increased in SI-NETs compared to normal ileum (P < 0.001). The telomerase reverse transcriptase gene (TERT) was over-expressed in SI-NETs vs. normal ileal samples (P = 0.01). Furthermore, relative TL assessed by qPCR was found shorter in tumours compared with normal ileum (P = 0.02) and in distant metastasis samples compared to primary tumours and local metastases (P= 0.02). TERT promoter hotspot mutations were not present and TERT copy number gain was only observed in 3/70 tumour samples. TERT or chromosome 18 copy number alterations were not associated with telomerase expression and activity or TL. However, hypermethylation of TERT promoter in Region B – in the proximity of the transcription start site – was inversely correlated with TERT expression and telomerase activity and positively correlated with TL. Global LINE1 methylation was positively correlated with TERT promoter Region B methylation and was inversely correlated with telomerase activity, TERT expression and the upstream Region A methylation. The results show that telomerase activation, TERT expression and shorter telomeres are commonly found in SI-NETs. Aberrant DNA methylation of TERT promoter and of LINE1 can be implicated in abnormal regulation of TERT in SI-NETs.

Abstract Background Follicular thyroid carcinoma (FTC) is a neoplasm that presents with a micro-follicular growth pattern and a neutrally stained cytoplasm. Seldom, FTCs display unusual morphological characteristics – but given the rarity of these histological subtypes, little is known regarding the underlying genetics and the coupling to patient outcome. Case presentation We present two extremely rare cases of minimally invasive FTC with signet ring cell morphology (SRC-FTC) and describe the cytological, microscopic, immunohistochemical and molecular features for both tumors. Both were male patients, age 71 and 51 respectively. The preoperative cytology for both cases could not pinpoint a clear-cut signet ring cell morphology, but a tendency towards nuclear marginalization was seen. The tumors were 38 mm and 22 mm respectively and displayed evident signet ring cell features in subsets of tumor cells as well as degenerative stromal changes. The tumor cells were positive for TTF1, PAX8 and thyroglobulin, and the proliferation indexes were 4% and 1,9% respectively. Both tumors displayed capsular invasion, but not lymphovascular invasion. The tumors were sequenced for mutations in the TERT promoter and 22 additional cancer-related genes, interestingly; one patient was shown to carry a deleterious intronic variant in PTEN, a tumor suppressor gene coupled to thyroid tumorigenesis and Cowden syndrome. Both patients are alive and well awaiting postoperative radioiodine treatment. Conclusions The SRC-FTCs described herein were small, TERT promoter wildtype tumors exhibiting low proliferation, thereby suggesting that these exceedingly rare lesions probably carry a favorable prognosis – although the scarce availability regarding descriptions of this tumor entity nevertheless might justify careful clinical monitoring and mandate investigations in larger case series.

PurposeNeuroendocrine tumors of the pancreas (Pan-NETs) are usually hormonally inactive with a capacity to metastasize. Since Pan-NETs are rare, more knowledge is needed.MethodsWe reviewed all patients’ medical files with Pan-NET treated at a tertiary center (2006-2019). Grade 1 (G1) and grade 2 (G2) tumors were compared. The latter group was subdivided arbitrarily based on proliferation index into G2a (3-9.9%) and G2b (10-19.9%).ResultsWe found 137 patients (76 females, 61 males; G1 n=66, G2 n=42), the median age at diagnosis 61 years (interquartile range (IQR) 50–71), and tumor size 2 cm (1.3–5 cm). The initial surgery was performed in 101 patients. The remaining (n=36) were followed conservatively. Metastatic disease was evident in 22 patients (16%) at diagnosis while new lesions developed in 13 out of 22 patients (59%). In patients without previous metastatic disease, progressive disease was discovered in 29% of G1 vs. 55% of G2 patients (P=0.009), 47% of G2a vs. 75% of G2b patients (NS). Survival was poorer in patients with metastasis at diagnosis vs. those with local disease (P

Abstract Background Papillary thyroid carcinoma with pleomorphic tumor giant cells (PTC-PC) is characterized by the occurrence of bizarre, pleomorphic cells within a small area of a conventional PTC. The histologic distinction between PTC-PC and PTC’s with a focal anaplastic thyroid cancer (ATC) component (denoted in the 2004 WHO classification as “papillary thyroid carcinoma with spindle and giant cell carcinoma”, PTC-SGC) is debated, however the prognosis is thought to be different (excellent for PTC-PC, poor for PTC-SGC). Therefore, this diagnostic challenge is significant for any endocrine pathologist to recognize. Herein, we report the histological and clinical workup of a PTC-PC case, with particular focus on the molecular analyses that facilitated the establishment of the final diagnosis. Case presentation The patient was a pregnant, 28-year-old female presenting with a 30 mm conventional PTC, with focal areas with undifferentiated cells exhibiting exaggerated nuclear pleomorphism. No foci of extrathyroidal extension, angioinvasion or lymph node engagement were seen. Immunohistochemical analyses revealed the pleomorphic cells exhibiting retained differentiation. Molecular genetic analyses demonstrated a codon V600 missense mutation of the BRAF gene, but no TP53 or TERT promoter mutations. The absence of an aggressive phenotype in addition to the lack of mutations in two major ATC-related genes led to the diagnosis of a PTC-PC. Postoperative MRI showed no evidence of metastatic disease. Radioiodine ablation was performed seven months post-operatively, and a SPECT-CT imaging did not show signs of residual tissue. She is well and without signs of disease 16 months post-operatively. Conclusions PTC-PC is a differential diagnosis to PTC-SGC that mandates careful considerations. Taken together with previous publications, PTC-PC seems to be histologically similar to PTC-SGC, but clinically distinct. Even so, the distinction is not easily made given the different therapeutic consequences for each individual patient. This is the first report that includes molecular genetics to aid in finalizing the diagnosis. Exclusion of mutations in TP53 and the TERT promoter could be considered as an adjunct tool when assessing papillary thyroid cancer with focal pleomorphism.

The diagnosis of parathyroid carcinoma requires an invasive growth pattern or metastases detected at histopathological examination; unfortunately, not all carcinomas exhibit visible malignant properties at the initial assessment. Therefore, immunohistochemical markers have been sought for the recognition of parathyroid malignancy. In 2003, the Hyperparathyroidism 2 (HRPT2) gene was found mutated in the majority of sporadic parathyroid carcinomas investigated, and studies regarding the protein product parafibromin proposed loss of nuclear parafibromin as a highly sensitive marker for the detection of parathyroid carcinoma. Recent studies have not fully reproduced these findings, as subsets of carcinomas display positive parafibromin immunoreactivity, and fractions of adenomas demonstrate absent expression. Overall, parafibromin is a marker of value to the endocrine pathologist, but it cannot be recommended as a sole indicator of parathyroid carcinoma. Additional markers such as protein gene product 9.5 (PGP9.5) and adenomatous polyposis coli (APC) could complement parafibromin when assessing malignant potential of parathyroid tumours.

Background: Successful radioiodine treatment of differentiated thyroid canc er requires iodine avidity: that is, the concentration and retention of iodine in cancer tissue. Several parameters have previously been linked with lower iodine avidity. However, a comprehensive analysis of which factors best predict iodine avidity status, and the magnitude of their impact, is lacking. Methods: Quantitative measurements of iodine avidity in surgical specimens (primary tumour and lymph node metastases) of 28 patients were compared to immunohistochemical expression of the thyroid-stimulating hormone receptor, thyroid peroxidase (TPO), pendrin, sodium–iodide symporter (NIS) and mutational status of BRAF and the TERT promoter. Regression analysis was used to identify independent predictors of poor iodine avidity. Results: Mutations in BRAF and the TERT promoter were significantly associated with lower iodine avidity for lymph node metastases (18-fold and 10-fold, respectively). Membranous NIS localisation was found only in two cases but was significantly associated with high iodine avidity. TPO expression was signific antly correlated with iodine avidity (r = 0.44). The multivariable modelling showed that tumour tissue localisation (primary tumour or lymph node metastasis), histological subtype, TPO and NIS expression and TERT promoter mutation were each independent predictors of iodine avidity that could explain 68% of the observed variation of iodine avidity. Conclusions: A model based on histological subtype, TPO and NIS expression and TERT promoter mutation, all evaluated on initial surgical material, can predict iodine avidity in thyroid cancer tissue ahead of treatment. This could inform early adaptation with respect to expected treatment effect.

Summary: Merkel cell carcinoma is an aggressive skin malignancy, mostly caused by Merkel cell polyomavirus (MCPyV). MCPyV T-antigens can induce mature microRNA expressions through the DnaJ domain, but its underlying mechanism is still unknown. Here, we report that the T-antigens induce protein expression and mRNA stability of DICER1, a key factor in microRNA biogenesis, through heat shock cognate 70 (HSC70). HSC70 directly interacts with the AU-rich elements (ARE) of DICER1 mRNA in both coding and 3′ untranslated region in the presence of MCPyV T-antigen. The T-antigen/HSC70 interaction could induce luciferase activity of synthetic ARE-containing reporter, as well as the stability of ARE-containing mRNAs, suggesting a broader role of MCPyV T-antigens in regulating multiple mRNAs via HSC70. These findings highlight a new role for the interaction of HSC70 and MCPyV T-antigens in mRNA regulation and an undescribed regulatory mechanism of DICER1 mRNA stability and translation through its direct interaction with HSC70.

Human cytochome P450 2W1 (CYP2W1) enzyme is expressed in fetal colon and in colon tumors. The level of expression is higher in colon metastases than in the parent tumors and the enzyme is a possible drug target for treatment of colorectal cancer, as demonstrated in mouse xenograft studies. A previous study published in this journal reported that CYP2W1 is highly expressed in normal and transformed adrenal tissue. However, adrenal expression of CYP2W1 protein was not seen in previous studies in our research group. To clarify this inconsistency, we have used qRT-PCR and Western blotting with CYP2W1-specific antibodies to probe a panel of 27 adrenocortical carcinomas and 35 normal adrenal cortex samples. CYP2W1 mRNA expression is seen in all samples. However, significant CYP2W1 protein expression was found in only one tumor sample (a testosterone-producing adrenocortical carcinoma) and not in any normal tissue. Differences in the specificity of the CYP2W1 antibodies used in the two studies may explain the apparent discrepancy. We conclude that normal adrenal tissue lacks P450 2W1 enzyme expression; also, adrenocortical carcinomas generally do not express the enzyme. This information thus underline the colon cancer specificity of CYP2W1 enzyme expression and has implications for the development of anti-colon cancer therapies based on CYP2W1 as a drug target, since 2W1-dependent bioactivation of prodrugs for CYP2W1 will not take place in normal adrenal tissue or other non-transformed tissues.

Many Mendelian traits are likely unrecognized owing to absence of traditional segregation patterns in families due to causation by de novo mutations, incomplete penetrance, and/or variable expressivity. Genome-level sequencing can overcome these complications. Extreme childhood phenotypes are promising candidates for new Mendelian traits. One example is early onset hypertension, a rare form of a global cause of morbidity and mortality. We performed exome sequencing of 40 unrelated subjects with hypertension due to primary aldosteronism by age 10. Five subjects (12.5%) shared the identical, previously unidentified, heterozygous CACNA1HM1549V mutation. Two mutations were demonstrated to be de novo events, and all mutations occurred independently. CACNA1H encodes a voltage-gated calcium channel (CaV3.2) expressed in adrenal glomerulosa. CACNA1HM1549V showed drastically impaired channel inactivation and activation at more hyperpolarized potentials, producing increased intracellular Ca2+, the signal for aldosterone production. This mutation explains disease pathogenesis and provides new insight into mechanisms mediating aldosterone production and hypertension.

Cystic papillary thyroid carcinoma (cPTC) is a subgroup of PTC presenting a diagnostic challenge at fine needle aspiration biopsy (FNAB). To further investigate this entity we aimed to characterize protein profiles of cyst fluids from cPTC and benign thyroid cystic lesions. In total, 20 cPTCs and 56 benign thyroid cystic lesions were studied. Profiling by liquid chromatography tandem mass spectrometry (LC-MS/MS) was performed on cyst fluids from a subset of cases after depletion, and selected proteins were further analyzed by Western blot (WB), immunohistochemistry (IHC) and enzyme-linked immunosorbent assay (ELISA). A total of 1,581 proteins were detected in cyst fluids, of which 841 were quantified in all samples using LC-MS/MS. Proteins with different expression levels between cPTCs and benign lesions were identified by univariate analysis (41 proteins) and multivariate analysis (59 proteins in an orthogonal partial least squares model). WB analyses of cyst fluid and IHC on corresponding tissue samples confirmed a significant up-regulation of cytokeratin 19 (CK-19/CYFRA 21-1) and S100A13 in cPTC vs. benign lesions. These findings were further confirmed by ELISA in an extended material of non-depleted cyst fluids from cPTCs (n = 17) and benign lesions (n = 55) (p55 ng/ml for CK-19 resulted in 82% specificity and sensitivity. For S100A13 a cut-off at >230 pg/ml revealed a 94% sensitivity, but only 35% specificity. This is the first comprehensive catalogue of the protein content in fluid from thyroid cysts. The up-regulations of CK-19 and S100A13 suggest their possible use in FNAB based preoperative diagnostics of cystic thyroid lesions.

Mutations in the hyperparathyroidism type 2 (HRPT2/CDC73) gene and alterations in the parafibromin protein have been established in the majority of parathyroid carcinomas and in subsets of parathyroid adenomas. While it is known that CDC73-mutated parathyroid tumors display specific gene expression changes compared to CDC73 wild-type cases, the molecular cytogenetic profile in CDC73-mutated cases compared to unselected adenomas (with an expected very low frequency of CDC73 mutations) remains unknown. For this purpose, nine parathyroid tumors with established CDC73 gene inactivating mutations (three carcinomas, one atypical adenoma and five adenomas) were analyzed for copy number alterations and loss of heterozygosity using array-comparative genomic hybridization (a-CGH) and single nucleotide polymorphism (SNP) microarrays, respectively. Furthermore, CDC73 gene promoter methylation levels were assessed using bisulfite Pyrosequencing. The panel included seven tumors with single mutation and three with double mutations of the CDC73 gene. The carcinomas displayed copy number alterations in agreement with previous studies, whereas the CDC73-mutated adenomas did not display the same pattern of alterations at loci frequently deleted in unselected parathyroid tumors. Furthermore, gross losses of chromosomal material at 1p and 13 were significantly (p = 0.012) associated with parathyroid carcinomas as opposed to adenomas. Quantitative PCR-based copy number loss regarding CDC73 was observed in three adenomas, while all the carcinomas were diploid or showed copy number gain for CDC73 gene. Hypermethylation of the CDC73 gene promoter was not observed. Our data could suggest that CDC73-mutated parathyroid adenomas exhibit a partly unique cytogenetic profile in addition to that of carcinomas and unselected adenomas. Furthermore, CDC73-mutated carcinomas displayed losses at 1p and 13 which are not seen in CDC73-mutated adenomas, making these regions of interest for further studies regarding malignant properties in tumors from CDC73-mutated cases. However, due to the small sample size, validation of the results in a larger cohort is warranted.

Primary hyperparathyroidism (PHPT) is an endocrine disorder most commonly affecting women, suggesting a role for female hormones and/or their receptors in parathyroid adenomas. We here investigated the prolactin receptor (PRLr) which is associated with tumours of the breast and other organs.PRLr expression was investigated in a panel of 37 patients with sporadic parathyroid tumours and its functionality in cultured parathyroid tumour cells. In comparison with other tissues and breast cancer cells, high levels of prolactin receptor gene (PRLR) transcripts were demonstrated in parathyroid tissues. PRLr products of 60/70 kDa were highly expressed in all parathyroid tumours. In addition varying levels of the 80 kDa PRLr isoform, with known proliferative activity, were demonstrated. In parathyroid tumours, PRLr immunoreactivity was observed in the cytoplasm (in all cases, n = 36), cytoplasmic granulae (n = 16), the plasma membrane (n = 12) or enlarged lysosomes (n = 4). In normal parathyroid rim (n = 28), PRLr was uniformly expressed in the cytoplasm and granulae. In in vitro studies of short-term cultured human parathyroid tumour cells, prolactin stimulation was associated with significant transcriptional changes in JAK/STAT, RIG-I like receptor and type II interferon signalling pathways as documented by gene expression profiling. Moreover, PRLR gene expression in parathyroid tumours was inversely correlated with the patients' plasma calcium levels.We demonstrate that the prolactin receptor is highly abundant in human parathyroid tissues and that PRLr isoforms expression and PRLr subcellular localisation are altered in parathyroid tumours. Responsiveness of PRLr to physiological levels of prolactin was observed in the form of increased PTH secretion and altered gene transcription with significant increase of RIG-I like receptor, JAK-STAT and Type II interferon signalling pathways. These data suggest a role of the prolactin receptor in parathyroid adenomas.

BackgroundParathyroid adenomas constitute the most common entity in primary hyperparathyroidism, and although recent advances have been made regarding the underlying genetic cause of these lesions, very little data on epigenetic alterations in this tumour type exists. In this study, we have determined the levels of promoter methylation regarding the four tumour suppressor genes APC, RASSF1A, p16(INK4A) and RAR-beta in parathyroid adenomas. In addition, the levels of global methylation were assessed by analyzing LINE-1 repeats.Methodology/principal findingsThe sample collection consisted of 55 parathyroid tumours with known HRPT2 and/or MEN1 genotypes. Using Pyrosequencing analysis, we demonstrate APC promoter 1A and RASSF1A promoter hypermethylation in the majority of parathyroid tumours (71% and 98%, respectively). Using TaqMan qRT-PCR, all tumours analyzed displayed lower RASSF1A mRNA expression and higher levels of total APC mRNA than normal parathyroid, the latter of which was largely conferred by augmented APC 1B transcription levels. Hypermethylation of p16(INK4A) was demonstrated in a single adenoma, whereas RAR-beta hypermethylation was not observed in any sample. Moreover, based on LINE-1 analyses, parathyroid tumours exhibited global methylation levels within the range of non-neoplastic parathyroid tissues.Conclusions/significanceThe results demonstrate that APC and RASSF1A promoter hypermethylation are common events in parathyroid tumours. While RASSF1A mRNA levels were found downregulated in all tumours investigated, APC gene expression was retained through APC 1B mRNA levels. These findings suggest the involvement of the Ras signaling pathway in parathyroid tumorigenesis. Additionally, in contrast to most other human cancers, parathyroid tumours were not characterized by global hypomethylation, as parathyroid tumours exhibited LINE-1 methylation levels similar to that of normal parathyroid tissues.