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Objectives To compare the performance of the rabbit monoclonal antihuman CD246 antibody (D5F3 clone) with the established ALK1 clone for immunohistochemical assessment of anaplastic large cell lymphoma (ALCL). Methods Archival cases of ALCL (n = 27) were assessed immunohistochemically by use of ALK1 and D5F3 clones under standard Clinical Laboratory Improvement Amendments–compliant conditions. The intensity of cytoplasmic staining (0 = none; 1 = faint; 2 = moderate; 3+ = strong) and proportion of neoplastic cells (0%, 50%) were evaluated and compared with clinical ALK break-apart fluorescence in situ hybridization (FISH) assays. Results Nine ALCL specimens were positive for ALK expression by ALK1 staining (33%; 1 = 1+; 0 = 2+; 8 = 3+), while 14 were positive by D5F3 staining (48%; 3 = 1+; 1 = 2+; 10 = 3+). Across the cohort, D5F3 staining showed a significantly greater proportion of cells staining positive (P = .02) and greater intensity (P = .03). Of 3 cases positive for D5F3 only with FISH results, none showed rearrangements, although 1 showed copy number gains at the ALK locus in a subset of cells. Conclusions Overall, D5F3 showed greater stain intensity and proportion staining than ALK1 in ALK-positive ALCL cases, which is especially helpful in limited samples. Caution and consideration of orthogonal ALK testing types is recommended, especially for cases with weak or focal staining.

ObjectivesUniversal screening of upper tract urothelial carcinoma (UTUC) for Lynch syndrome by mismatch repair (MMR) protein immunohistochemistry (IHC) has been recommended by some investigators. Herein, we assess this recommendation retrospectively by simulating its performance on a retrospective, unselected cohort of UTUCs, with comparison to the established setting of colorectal and endometrial adenocarcinoma.MethodsWe assessed for complete loss of MMR protein (MLH1, MSH2, MSH6, and PMS2) IHC in 74 consecutive cases of UTUC and then tabulated clinical and pathologic factors. MMR findings from same-institution colorectal and endometrial adenocarcinomas were tabulated for comparison.ResultsWe observed loss of at least one MMR protein in 12% in our UTUC cohort (three MSH2/MSH6, three MSH6 only, one MLH1/PMS2, and two PMS2 only). Of these nine cases (seven males, two females, median age 67 years, five associated with colorectal adenocarcinoma), at least three (4% of the overall cohort) proved to be Lynch syndrome. Overall, MMR loss in UTUC was comparable to colorectal (11%; 50 of 471 cases) and endometrial (12%; 12 of 101 cases) adenocarcinomas.ConclusionsThe rate of MMR loss observed in UTUC was comparable to that in the established setting of colorectal and endometrial adenocarcinomas, supporting universal UTUC screening at our institution and others.

Objectives Superficial pleomorphic liposarcoma (PL) has a favorable prognosis compared to deeply seated PL. Given developments in the classification of lipomatous neoplasms, we reappraised a series of cases. Methods Retrospective clinicopathologic evaluation and genome-wide single-nucleotide polymorphism (SNP) microarray studies were performed for cases previously designated superficial PL. Results Four cases were identified (age, 48-70 years). Two were dermally confined, whereas two were superficial subcutaneous; no recurrences or metastases were reported. Tumors demonstrated pleomorphic spindled morphology with variable cellularity. Multivacuolated atypical lipoblasts were focal in 3 and abundant in 1. Dermal tumors demonstrated atypical cells within sclerotic collagen. Genome-wide SNP microarray studies revealed consistent gains and losses, including losses at the 13q14.2 locus encompassing RB1 and DLEU2 and deletion/disruption of the TP53 locus. Although subcutaneous examples showed genomic changes similar to deep PL, the dermal examples showed fewer genetic alterations, including changes reported in the spectrum of atypical spindle cell/pleomorphic lipomatous tumors (ASPLT). All lacked MDM2 amplification. Conclusions Careful integration of histologic and genetic features may improve classification of lipomatous neoplasms with atypia, allowing reclassification of some superficial PL as ASPLT.

Introduction/Objective Germline mutations in the tumor suppressor gene Armadillo-containing repeat protein 5 gene (ARMC5) have been very recently recognized as a cause for a familial form of bilateral macronodular adrenocortical hyperplasia (BMAH), itself a rare cause of Cushing syndrome. In patients with ARMC5 mutations, scattered case reports have also shown an association with meningiomas and cancers of the pancreas, breast, colon, and thyroid. Methods/Case Report We present the case of BMAH, arising in a 61-year-old female with a history of metastatic papillary thyroid carcinoma and meningioma. The patient presented with bilateral but asymmetric adrenal enlargement (right greater than left) and Cushing syndrome. Given history of thyroid cancer and meningioma, genetics referral was ordered. Counseling revealed a pedigree without a strongly evident familial pattern of hereditary endocrine neoplasia characteristic of any of the more common inherited dispositions to endocrine neoplasia. Additionally, a targeted capture-based NGS germline genetic sequencing study for variants in 12 genes associated with associated with hereditary thyroid cancer was performed and negative. However, based on recent scholarship regarding ARMC5, follow-up germline NGS and Sanger sequencing studies encompassing the entire coding sequences of ARMC5 were ordered. These identified a germline, heterozygous, novel (not in ClinVar) but likely pathogenic variant in (c.802C>T, p.Arg268*), providing a likely explanation for the patient’s BMAH. In attempt to control the patient’s Cushing symptoms, right-sided adrenalectomy was performed, revealing a 220g adrenal gland with marked multinodular hyperplasia with solid, nested, and tubular architecture. Results (if a Case Study enter NA) NA Conclusion While case reports exist describing an association between other ARMC5 mutations and BMAH with concomitant meningiomas and/or malignancies, greater study is needed in order to better characterize the phenotypic spectrum of this disease. Our experience with this case not only reports a novel, apparently pathogenic mutation, but it documents its association with BMAH and, additionally, papillary thyroid carcinoma and meningioma.

Casestudy Gastroblastoma is a rare tumor with biphasic components showing epithelial and mesenchymal differentiation. To date, Results A CT scan was performed, showing a 7 cm heterogeneous mass in the distal stomach and pancreas, clinically suspected to represent at gastrointestinal stromal tumor (GIST). She underwent two preoperative samples, including endoscopic ultrasound guided-fine needle aspiration and core biopsy, followed by a distal gastrectomy. Diff- Quik stained touch preparations performed on the core needle biopsy during rapid on-site evaluation showed a hypercellular neoplasm composed of large, three-dimensional aggregates of neoplastic cells in a background of numerous isolated single cells and bare nuclei. The neoplastic cells were bland with spindled to epithelioid nuclei, occasional nuclear grooves, and small nucleoli. Immunostains were only helpful in excluding GIST (CD117 and DOG1 negative). Distal gastrectomy showed a nodular/plexiform tumor with variably epithelioid to spindle cell cytology and solid to focally myxoid/microcystic architecture. Pancytokeratins CAM5.2 (patchy) and AE1/AE3 (very focal) were positive, with negative S100, SMA, Desmin, Melan-A, Inhibin, Calretinin, and Synaptophysin. Based on the age, location, histology and immunophenotype, gastroblastoma was suspected, and multiplex NGS-based fusion sequencing identified a MALAT1-GLI1 fusion. Staging studies were negative for metastasis at presentation. Conclusion Based on this experience, we recommend consideration of gastroblastoma for a gastric tumor in a young patient, especially if encountering a cytologic sample showing non-pleomorphic epithelioid and spindle cell cytology. Lack of expression of GIST, smooth muscle, neuroendocrine, and neural sheath-associated markers should particularly raise consideration of this rare neoplasm. While in this case molecular studies clinched the diagnosis upon resection, increasingly used GLI1 immunostain may be of use prospectively for diagnosis of limited samples.

Objectives: New immunohistochemical (IHC) markers of urothelial carcinoma (UCa) and prostatic adenocarcinoma (PCa) have emerged in recent years, yet comparative studies to establish markers remain lacking. We aimed to identify an effective but parsimonious approach for poorly differentiated bladder neck lesions, to establish a best practice panel approach in a setting simulating prospective use. Methods: We tested the performance of a panel of IHC markers on whole sections of a consecutive cohort of transurethral resection specimens of poorly differentiated, challenging bladder neck resections (n = 36). Results: In the setting of poorly differentiated bladder neck carcinomas, biomarker sensitivities for UCa were as follows: GATA3, 100%; S100P, 88%; p63, 75%; and cytokeratin (CK) 5/6, 56%; specificities of each were 100%. CK7 and CK20 showed sensitivities of 75% and 63%, though these were only 85% and 80% specific. For PCa markers, NKX3.1, p501S, prostate-specific membrane antigen, and androgen receptor (AR) each showed 100% sensitivity, outperforming ERG (35%) and prostate-specific antigen (PSA; 25%). All the prostate histogenesis markers were 100% specific, except for AR, which was positive in 13% of the UCa cases. Conclusions: Novel IHC markers show improved diagnostic performance that enables positive and negative support for identifying histogenesis with the use of as few as two markers for this critical therapeutic distinction. PSA underperforms newer markers.