C19MC amplification and expression of Lin28A and Olig2 in the classification of embryonal tumors of the central nervous system: A 14-year retrospective study from a tertiary care center.

INTRODUCTION: CNS embryonal tumors (CET) other than medulloblastomas (MB) and atypical teratoid/rhabdoid tumors (AT/RTs), previously designated as 'central nervous system primitive neuroectodermal tumors' ('CNS PNETs'), are a heterogenous subset of tumors with poorly defined diagnostic criteria. Other than the subset of embryonal tumor with multilayered rosettes (ETMR) defined by C19MC amplification, most CETs are diagnosed by exclusion of other molecularly defined entities and histological mimics including MB, AT/RTs, and high-grade gliomas, and termed as CET, not otherwise specified (NOS) in the 2016 WHO classification. AIM: To reclassify 'CNS PNETs' as per WHO 2016, and estimate the true proportion of CET, NOS in a tertiary healthcare setting, and to evaluate the diagnostic utility of C19MC amplification, Lin28A and Olig2 expression in the subclassification of CETs. METHODS: Previously diagnosed cases of 'CNS PNETs' (2002-2016) were first evaluated by immunohistochemistry (IHC) for MIC2, RelaA, L1CAM, IDH1R132H, H3K27M, H3G34R, H3G34V, INI1, and BRG1 proteins and by fluorescence in-situ hybridization (FISH) for EWSR1 translocation to exclude histological mimics. The selected CETs (case cohort) and 79 histological mimics (comparison cohort) comprising of MB, AT/RT, pineal parenchymal tumors, Ewing sarcoma, esthesioneuroblastoma, intraocular medulloepithelioma, and H3G34R mutant high-grade glioma were subject to IHC for Olig2 and Lin28A, and FISH for C19MC amplification. RESULTS: Twenty-two cases of 'CNS PNETs' were retrieved, all of which were negative for the first panel of markers and showed retained INI-1/BRG1 expression. Three of them (3/22, 13.6%) showed C19MC amplification (ETMR, C19MC-altered) with ETMR histology, Lin28A positivity, and Olig2 negativity. Among the remaining 19 CETs, one showed medulloepithelioma histology (Medulloepithelioma, NOS) and remaining were non-descript small round cell tumors (CET, NOS), all negative for Lin28A. Olig2 was positive in only 3 CETs (13.6%), all being CET, NOS. All tumors in the comparison cohort were negative for C19MC amplification, Lin28A and Olig2 except for 27% of ATRTs that were Lin28A positive. CONCLUSION: ETMR, C19MC-altered constitute less than 14% of CETs, with majority remaining uncharacterized as CET, NOS. Lin28A is 100% sensitive for the detection of C19MC amplification; however, its specificity is limited by its expression in ATRTs. Olig2 expression is seen only in a small subset of CET, NOS and is of limited diagnostic utility.

Segmental filiform-polyposis in a treated case of ulcerative colitis, colon: An unusual presentation raising a doubt of primary diagnosis?

Inflammatory bowel disease is broadly classified into Crohn's disease and ulcerative colitis. The standard criteria to distinguish between the two is the manner of the involvement of the bowel, with the former showing classical skip lesions and the latter having continuous involvement of the colon, most commonly affecting the rectum. However, some cases exhibit overlapping features. Herein, we report a treated case of ulcerative colitis presenting with patchy involvement of the colon in the form of peculiar segmental filiform polyposis spanned abruptly by an intervening normal mucosa. The clinico-radiologically suspicion of carcinoma colon with Crohn's colitis was considered. The clinicians and pathologists must be aware of such atypical presentations and should not be misled to change the diagnosis from ulcerative colitis to Crohn's colitis on the post-treatment resection specimens or endoscopic biopsies solely in view of the patchy filiform polyposis (FP), which poses a drastic impact on the patient's management.

Reappraisal of SWI/SNF-related matrix-associated actin-dependent regulator of chromatin subfamily B member 1/INI-1 deficient tumor: Report of two cases.

SWI/SNF-related matrix-associated actin-dependent regulator of chromatin subfamily B member 1 is a tumor suppressor gene located at chromosome 22q11.2. In the past decade, a major stride has been taken for decoding the molecular genesis of various tumors which has resulted in the addition of newer tumors harboring loss of this gene.

Extranodal Follicular dendritic cell sarcoma presenting as a rectal polyp: An entity overlooked by its differentials.

Extranodal follicular dendritic cell sarcoma (ENFDCS) is a rare hematolymphoid tumor, masquerading as soft tissue sarcoma on initial histological examination. So, for its confirmation, the application of immunohistochemistry (IHC) is of paramount importance. Over the years there has been a major shift in the demography of follicular dendritic cell sarcoma (FDCS), with a rise in the number of extranodal cases. Herein we report a case of ENFDCS presenting as a rectal polyp, who had a history of intermittent bleeding per rectum and passage of fleshy mass while defecation. As these tumors share an overlapping morphology with other spindle cell tumors and can occur at unpredictable locations, they pose a diagnostic challenge, especially for young pathologists.

Uterine tumor resembling ovarian sex cord tumor: A series of six cases displaying varied histopathological patterns and clinical profiles.

INTRODUCTION: Uterine tumors resembling ovarian sex cord tumor (UTROSCT) are a unique group of neoplasms with diverse morphology and immunophenotypic characteristics, coexpressing sex cord, epithelial, and smooth-muscle markers. To date, less than 100 cases have been reported and there is paucity of data concerning their clinical behavior. MATERIALS AND METHODS: All cases of uterine body tumors diagnosed over a period of two and a half years (2016-2018) were retrieved. Histopathological features were reviewed and extended panel of immunohistochemistry was performed to identify cases of UTROSCTs. RESULTS: Six cases of UTROSCTs were identified with a median age of 46.5 years. Four of them presented with menorrhagia, while two with postmenopausal bleeding including one with a history of carcinoma breast. Three of these cases were initially misdiagnosed as endometrial stromal sarcoma and adenocarcinomas. They all underwent hysterectomy with bilateral salpingo-oophorectomy. CONCLUSION: It is considered a tumor with low malignant potential; however, one out of six cases (16.7%) in our study showed metastasis, within 1 year of diagnosis. It is important to recognize this entity as it mimics a wide range of both benign and malignant tumors. Molecular pathogenesis and exact management protocols remain elusive due to rarity,hence, multi-institutional studies are warranted.