Perivascular epithelioid cell tumors (PEComa) are rare neoplasms characterized by co-expression of melanocytic and muscle markers. HMB45 and Melan-A are used to confirm a PEComa diagnosis; however, both are often focally expressed and sensitivity for Melan-A is low. PNL2 is a reliable biomarker for epithelioid melanoma and renal angiomyolipoma/PEComa. The objective of this study was to determine PNL2 utility in diagnosing uterine PEComas as well as distinguishing PEComas from uterine smooth muscle tumors (SMTs). Twenty-one uterine PEComas and 45 SMTs were analyzed for PNL2; a subset was also stained for HMB45, Melan-A, Cathepsin-K, Desmin, and h-Caldesmon. Cases were scored as negative (0), focal (<10% of tumor cells), or patchy to diffusely positive (>10% of tumor cells). PEComas were positive for PNL2, HMB45, and Melan-A in 86%, 100%, and 57% of cases, respectively. In PEComas, PNL2 was patchy to diffusely positive more frequently (10/18, 56%) than Melan-A (4/12, 33%). In contrast, 2 of 45 (4%) SMTs were focally PNL2 positive; HMB45 was focally positive in 4 SMTs (11%) and all were negative for Melan-A. Desmin and h-Caldesmon were positive in 90% and 57% of PEComas, and 91% and 82% of SMTs. Cathepsin-K was positive in 100% of PEComas and 93% of SMTs. PNL2 is a useful biomarker for the diagnosis of uterine PEComa, with comparable sensitivity and specificity to HMB45. In contrast, PNL2 stains more PEComas when compared with Melan-A. Cathepsin-K, Desmin, and h-Caldesmon are of little utility for distinguishing PEComas and SMTs; however, lack of Cathepsin-K argues against PEComa. These results suggest that PNL2 should be used in conjunction with HMB45 in the diagnosis of PEComa of the uterine corpus.

Understanding the transcription factors that modulate epithelial resistance to injury is necessary for understanding intestinal homeostasis and injury repair processes. Recently, transcription factor EB (TFEB) was implicated in expression of autophagy and host defense genes in nematodes and mammalian cells. However, the in vivo roles of TFEB in the mammalian intestinal epithelium were not known. Here, we used mice with a conditional deletion of Tfeb in the intestinal epithelium (Tfeb ΔIEC) to examine its importance in defense against injury. Unperturbed Tfeb ΔIEC mice exhibited grossly normal intestinal epithelia, except for a defect in Paneth cell granules. Tfeb ΔIEC mice exhibited lower levels of lipoprotein ApoA1 expression, which is downregulated in Crohn’s disease patients and causally linked to colitis susceptibility. Upon environmental epithelial injury using dextran sodium sulfate (DSS), Tfeb ΔIEC mice exhibited exaggerated colitis. Thus, our study reveals that TFEB is critical for resistance to intestinal epithelial cell injury, potentially mediated by APOA1.

Context.— Tumor histology offers a composite view of the genetic, epigenetic, proteomic, and microenvironmental determinants of tumor biology. As a marker of tumor histology, histologic grading has persisted as a highly relevant factor in risk stratification and management of urologic neoplasms (ie, renal cell carcinoma, prostatic adenocarcinoma, and urothelial carcinoma). Ongoing research and consensus meetings have attempted to improve the accuracy, consistency, and biologic relevance of histologic grading, as well as provide guidance for many challenging scenarios. Objective.— To review the most recent updates to the grading system of urologic neoplasms, including those in the 2016 4th edition of the World Health Organization (WHO) Bluebook, with emphasis on issues encountered in routine practice. Data Sources.— Peer-reviewed publications and the 4th edition of the WHO Bluebook on the pathology and genetics of the urinary system and male genital organs. Conclusions.— This article summarizes the recently updated grading schemes for renal cell carcinoma, prostate adenocarcinomas, and bladder neoplasms of the genitourinary tract.

Direct immunofluorescence (DIF) on frozen tissue (DIF-F) is the method of choice for the identification of immune deposits present in skin and other tissues. DIF can also be performed on formalin-fixed paraffin-embedded tissue (DIF-P) after antigen retrieval with proteases and has proven to be of value in renal pathology. However, its utility in skin biopsies has not been fully examined. In this study, we performed DIF-P on 60 skin biopsies that comprised of bullous pemphigoid (n = 18), pemphigoid gestationis (n = 1), pemphigus (n = 7), linear IgA disease (n = 7), vasculitis (n = 20), lupus erythematosus (n = 3), and dermatitis herpetiformis (n = 4) cases. We compared the results of DIF-P with those of DIF-F from the same patients. The diagnostic features were found in 15 of 19 (79%) pemphigoid (bullous pemphigoid and pemphigoid gestationis), 3 of 7 (43%) pemphigus, 3 of 7 (43%) linear IgA disease, 14 of 20 (70%) vasculitis, 1 of 3 (33%) lupus erythematosus, and none (0%) of the dermatitis herpetiformis cases tested. Overall, DIF-P is less sensitive than DIF-F but seems to be a valuable technique that could aid in the diagnosis of vasculitides, immunobullous, and connective tissue disorders when fresh tissue is unavailable.

The distinction between primary adnexal carcinoma (PAC) from metastatic breast carcinoma (BrCa) to skin and squamous cell carcinoma (SCC), particularly those with ductal differentiation (SCCDD), can be quite challenging, despite adequate history. The aim of the study was to determine the utility of an immunohistochemistry (IHC) panel to differentiate these entities and apply them to ambiguous tumors. Twenty-seven PAC, 7 metastatic BrCa, 28 SCC, and 16 ambiguous cases (SCCDD vs. PAC, n = 13 and metastatic BrCa vs. PAC, n = 3) were analyzed using CD23, PAX5, D2-40, P63, and CD117 immunohistochemistry. A total of 9 (33%) PAC were CD117 positive, whereas all metastatic BrCa and SCC were negative (P = 0.0002). D2-40 was expressed in 16 (59%) PAC and 16 (57%) SCC cases, but none of the metastatic BrCa cases (P = 0.0041). Of the 13 ambiguous tumors with a differential diagnosis of SCCDD versus PAC, all were positive for P63, 10 were positive for D2-40, and 1 was positive for CD117. Of the 3 ambiguous tumors with a differential diagnosis of PAC versus metastatic BrCA, 2 were positive for CD117, whereas none showed reactivity for D2-40 or P63. All cases were negative for CD23 and PAX5. Our study indicates that CD117 reactivity favors a PAC with a sensitivity and specificity of 33% and 100%, respectively. D2-40 and P63 expression highlighted both PAC and SCC and seems to be useful in excluding metastatic BrCa with a sensitivity and specificity of 58% and 100%, and 98% and 100%, respectively. Despite previous reports, CD23 and PAX5 do not seem to be useful.

Secondary tumors of the thyroid are quite rare with an estimated prevalence of < 1%. Herein, we describe the incidental discovery of metastatic small cell lung cancer in a non-toxic multinodular goiter. A 57-year-old lady has had a non-toxic multinodular goiter for over 10 years. She has had two thyroid fine needle aspirations (FNAs) in the past, which were reported benign. As the goiter was increasing in size and causing compression, she underwent a total thyroidectomy. Pathology revealed multi-centric high grade carcinoma with small cell/neuroendocrine features with the largest focus being 1.1 cm. Calcitonin staining was negative. Further imaging revealed a 68 × 37 × 51 mm soft tissue mediastinal mass and an 18 × 10 mm left upper lobe pulmonary nodule. She was then initiated on chemotherapy and radiation therapy for extensive stage small cell cancer of the lung. After two cycles of chemotherapy, restaging chest computed tomography (CT) showed interval improvement in lung masses. This rare presentation of small cell lung cancer with multi-centric metastasis to the thyroid highlights the need to obtain nodule directed FNAs, as the two non-directed FNAs done prior to surgery were benign. It also points out to clinicians that rapidly growing goiters are a cause for concern, and should be evaluated, even if patients are not symptomatic.

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Aims Perinephric fat invasion (PFI) is a key component of renal cell carcinoma (RCC) staging, but there are limited data pertaining to biopsy tract seeding (BTS) resulting in perirenal tissue involvement [BTS with perinephric fat invasion (BTS‐P)].The aim is to correlate clinical outcomes with pathologic stage to determine whether the presence of BTS‐P should be considered a criterion to stage RCC as part of the pT3a category in the absence of any other upstaging variables. Materials and results We identified 304 renal biopsies from patients with subsequent nephrectomies for RCC; 33 of the tumours contained PFI. Each case was reviewed to determine the presence of BTS‐P and other forms of invasion [e.g. non‐BTS‐P PFI, sinus fat invasion (SFI), and/or renal vein invasion (RVI)], and these findings were compared with survival outcomes. Ten (30%) of 33 tumours with PFI showed BTS‐P as the only finding, and were otherwise pT1 tumours; six (60%) patients were alive without disease (AWOD) (mean, 77.5 months), three were lost to follow‐up (LTF), and one died of other disease (DOOD). Two patients showed true PFI plus BTS‐P; one was LTF and one is AWOD at 107 months. Ten (43%) of 23 patients with tumours with true invasion (PFI ± SFI and/or RVI) are AWOD (mean, 97.7 months), eight (35%) died of disease (DOD), four were LTF, and one DOOD. Kaplan–Meier survival curves showed that the cancer‐specific survival was significantly worse in patients with true invasion (P = 0.044) than in those with BTS‐P as the sole finding. Conclusion Patients with tumours showing BTS‐P only appear to have better outcomes than those with other non‐PFI invasion, suggesting that this finding should not be upstaged to pT3a. Additional studies are needed to corroborate the significance of our observations.