The Cancer Genome Atlas described four major genomic groups of endometrial carcinomas, including a POLE ultramutated subtype comprising B10% of endometrioid adenocarcinoma, characterized by POLE exonuclease domain mutations, ultrahigh somatic mutation rates, and favorable outcome. Our aim was to examine the morphological and clinicopathological features of ultramutated endometrial carcinomas harboring somatic POLE exonuclease domain mutations. Hematoxylin and eosin slides and pathology reports for 8/17 POLEmutated endometrial carcinomas described in the Cancer Genome Atlas study were studied; for the remaining cases, virtual whole slide images publicly available at cBioPortal (www.cbioportal.org) were examined. A second cohort of eight POLE mutated endometrial carcinomas from University of Calgary was also studied. Median age was 55 years (range 33-87 years). Nineteen patients presented as stage I, 1 stage II, and 5 stage III. The majority of cases (24 of the 25) demonstrated defining morphological features of endometrioid differentiation. The studied cases were frequently high grade (60%) and rich in tumor-infiltrating lymphocytes and/or peri-tumoral lymphocytes (84%); many tumors showed morphological heterogeneity (52%) and ambiguity (16%). Foci demonstrating severe nuclear atypia led to concern for serous carcinoma in 28% of cases. At the molecular level, the majority of the Cancer Genome Atlas POLE-mutated tumors were microsatellite stable (65%), and TP53 mutations were present in 35% of cases. They also harbored mutations in PTEN (94%), FBXW7 (82%), ARID1A (76%), and PIK3CA (71%). All patients from both cohorts were alive without disease, and none of the patients developed recurrence at the time of follow-up (median 33 months; range 2-102 months). In conclusion, the recognition of ultramutated endometrial carcinomas with POLE exonuclease domain mutation is important given their favorable outcome. Our histopathological review revealed that these tumors are commonly high grade, have obvious lymphocytic infiltrates, and can show ambiguous morphology. As they frequently harbor TP53 mutations, it is important not to misclassify them as serous carcinoma.

Objective: To map the occurrence of amyloid types in a large clinical cohort using mass spectrometry-based shotgun proteomics, an unbiased method that unambiguously identifies all amyloid types in a single assay. Methods: A mass spectrometry-based shotgun proteomics assay was implemented in a central reference laboratory. We documented our experience of typing 16,175 amyloidosis specimens over an 11year period from January 1, 2008, to December 31, 2018. Results: We identified 21 established amyloid types, including AL (n¼9542; 59.0%), ATTR (n¼4600; 28.4%), ALECT2 (n¼511; 3.2%), AA (n¼463; 2.9%), AH (n¼367; 2.3%), AIns (n¼182; 1.2%), KRT5-14 (n¼94; <1%), AFib (n¼71; <1%), AApoAIV (n¼57; <1%), AApoA1 (n¼56; <1%), AANF (n¼47; <1%), Ab2M (n¼38; <1%), ASem1 (n¼34; <1%), AGel (n¼29; <1%), TGFB1 (n¼29; <1%), ALys (n¼15; <1%), AIAPP (n¼13; <1%), AApoCII (n¼11; <1%), APro (n¼8; <1%), AEnf (n¼6; <1%), and ACal (n¼2; <1%). We developed the first comprehensive organ-by-type map showing the relative frequency of 21 amyloid types in 31 different organs, and the first type-by-organ map showing organ tropism of 18 rare types. Using a modified bioinformatics pipeline, we detected amino acid substitutions in cases of hereditary amyloidosis with 100% specificity. Conclusion: Amyloid typing by proteomics, which effectively recognizes all amyloid types in a single assay, optimally supports the diagnosis and treatment of amyloidosis patients in routine clinical practice.

POEMS is an uncommon syndromic disorder characterized by polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, and skin changes. There are few descriptions of the bone marrow pathology of POEMS; therefore, peripheral blood smears and bone marrow aspirates and biopsies from 87 patients (143 total, 67 pretreatment, 76 posttreatment cases) with POEMS were studied. Plasma cell clonality was analyzed by flow cytometry, immunohistochemistry, and/or in situ hy-

TFE3 translocation associated PEComa is a distinct form of perivascular epithelioid cell neoplasm, the features of which are poorly defined owing to their general infrequency and limited prior reports with confirmed rearrangement or fusion totaling nine cases. Recent investigation has found a lack of TSC gene mutation in these tumors compared to their nonrearranged counterparts which underscores the importance of recognizing the translocated variant due to hypothetical ineffectiveness of targeted mTOR inhibitor therapy. Six cases were identified and TFE3 rearrangement was confirmed by FISH. Patient age ranged 46 to 66 years (median 50) and none had a history of tuberous sclerosis complex. Three cases arose in the uterine corpus, one in the vagina, and one pelvic tumor and one pulmonary tumor were likely a recurrence/metastasis from a probable uterine primary. Five cases had purely clear cell epithelioid morphology that showed a spectrum of atypia while one case had a mixture of clear cell epithelioid and spindle cells. A mostly consistent immunophenotype was observed in the purely clear cell epithelioid cases: each demonstrated diffuse TFE3, HMB45, CathepsinK labeling, either focal or no melanA staining and variably weak reactivity to smooth muscle markers. The mixed clear cell epithelioid and spindle cell case had a similar pattern in its epithelioid component, but strong muscle marker positivity in its spindle cell component. Follow up ranged 1 to 57 months. Three cases demonstrated aggressive behavior and three cases had no evidence of recurrence. Both GYN-specific and traditional sets of criteria for malignancy were evaluated. The GYN model showed improved inclusion and specificity in comparison to the traditional model.

Systemic anaplastic large cell lymphomas (ALCLs) are classified into ALK-positive and ALK-negative types. We recently reported that ALK-negative ALCLs are genetically heterogenous. The largest subset, representing 30% of cases, had rearrangements of the DUSP22 locus. These cases had favorable outcomes similar to ALK-positive ALCL, and superior to other ALK-negative ALCLs. Here, we examined the morphologic features of these cases in more detail. First, we conducted blinded review of hematoxylin and eosin slides of 108 ALCLs from our previous study, scoring cases for the presence of 3 histologic patterns and 5 cell types. Cases then were unblinded and re-reviewed to understand these features further. DUSP22-rearranged ALCLs were more likely than other ALK-negative ALCLs to have so-called doughnut cells (23% vs. 5%; P = 0.039), less likely to have pleomorphic cells (23% vs. 49%; P = 0.042), and nearly always (95%) had areas with sheet-like growth (common pattern). To examine the reproducibility of these findings, we conducted blinded review of hematoxylin and eosin slides of 46 additional ALK-negative ALCLs using a 0 to 3 scoring system to predict likelihood of DUSP22 rearrangement, the results of which correlated strongly with subsequent findings by fluorescence in situ hybridization (P < 0.0001). Although all ALCLs share certain morphologic features, ALCLs with DUSP22 rearrangements show significant differences from other ALK-negative ALCLs, typically showing sheets of hallmark cells with doughnut cells and few large pleomorphic cells. These morphologic findings and our previous outcome data suggest that ALK-positive ALCLs and DUSP22-rearranged ALCLs represent prototypical ALCLs, whereas ALCLs lacking rearrangements of both DUSP22 and ALK require further study.

The traditional model of hematopoiesis is based on unidirectional maturation of hematopoietic precursors into lineage-committed cells. However, recent studies indicate that mature B lymphocytes may demonstrate significant lineage plasticity. We and others have reported transdifferentiation of follicular lymphomas (FLs) into clonally related histiocytic/dendritic cell neoplasms. Here, we describe 2 patients with FL who developed clonally related Langerhans cell neoplasms. The first was a 52-year-old man diagnosed with FL, grade 1. He received immunochemotherapy and had stable disease for 8 years. He then developed increasing lymphadenopathy, and lymph node biopsy showed Langerhans cell sarcoma with no evidence of FL. The second patient was a 77-year-old woman who presented with lymphadenopathy, an abdominal mass, and pulmonary nodules. Lymph node biopsy showed both Langerhans cell histiocytosis and minimal involvement by FL, grade 1. In each case, a combination of immunoglobulin gene rearrangement and fluorescence in situ hybridization studies provided evidence to support a clonal relationship between the FL and Langerhans cell neoplasm. These cases provide striking examples of neoplastic transdifferentiation and expand the spectrum of lesions clonally identical to otherwise typical FL. Awareness of this phenomenon may aid in diagnosis when histologically dissimilar tumors arise synchronously or metachronously in patients with lymphoma.

Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) is a low-grade B-cell neoplasm and ∼2% to 9% patients develop an aggressive lymphoma, most commonly diffuse large B-cell lymphoma (Richter transformation, DLBCL-RT). Programmed death-1 (PD-1) pathway plays a crucial role in tumor host immunity evasion and its blockade has emerged as an effective anti-cancer immunotherapy. PD-L1 and PD-1 expression has shown predictive value in anti-PD cancer immunotherapy; however, it has not been well documented in CLL/SLL and DLBCL-RT. We evaluated PD-1 and PD-L1 expression by immunohistochemistry in 39 CLL/SLL, 15 DLBCL-RT, and 26 other DLBCL. In CLL/SLL, neoplastic B-cell PD-1 expression was weak and restricted to prolymphocytes/paraimmunoblasts within proliferation centers (PCs) and accentuated PCs of all sizes. Neoplastic B-cell PD-1 expression was highly prevalent and demonstrated increased intensity in DLBCL-RT, but in contrast was only rarely seen in other DLBCL (12/15 vs. 1/26; P<0.0001). An excellent correlation (90% concordance) was observed between neoplastic B-cell PD-1 immunohistochemistry positivity and molecularly defined CLL/SLL clonal relatedness in DLBCL-RT. PD-L1 expression was observed on the neoplastic B cells in rare DLBCL-RT and other DLBCL cases (1/15 vs. 1/26; P>0.05) as well as background histiocytes and dendritic cells. Overall survival of DLBCL-RT was significantly inferior to that of the other DLBCL (median, 16.9 vs. 106.1 mo; P=0.002). Our findings suggest a biological continuum from prolymphocytes/paraimmunoblasts in CLL/SLL PCs to the neoplastic B-cells in DLBCL-RT. The characteristic PD-1 expression in DLBCL-RT makes it a potential surrogate marker for determining clonal relatedness to CLL/SLL, which may have important prognostic and therapeutic implications.

Immunosuppressive medications, frequently used to treat inflammatory bowel disease, have been linked to the development of Epstein-Barr virus (EBV)-associated lymphoproliferative disorders (LPD). We describe a case of an EBV-positive mucocutaneous ulcer involving the palate in an elderly woman with inactive Crohn’s disease. This patient had been on high-dose azathioprine for a decade. Following diagnosis of her LPD and discontinuation of azathioprine, her oral ulcers resolved completely.