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Endometriosis involving the uterine cervix is a rare condition that can lead to diagnostic errors in the interpretation of Pap smear. We report the case of a 41 -year-old patient in whom the initial Pap smear revealed three-dimensional clusters of glandular cells with elongated nuclei, occasional mitosis, and atypia, which was interpreted as atypical glandular cells, not otherwise specified (NOS). The patient was taken to colposcopy and endocervical biopsy. Colposcopy was normal and the biopsy presented glands with elongated nuclei and surrounded by endometrial stroma admixed with normal endocervical glands. Immunohistochemical studies were reactive for CD10 in the stromal cells and vimentin in endometrioid glands. The findings were consistent with cervical endometriosis. Endometriosis in the cervix is an uncommon pathology that mimics malignancy and may be interpreted as atypical or glandular neoplasia in the cytology. [ABSTRACT FROM AUTHOR]

The diagnosis and treatment of sinonasal small round epithelial/neuroepithelial malignancies depends on the expression of conventional neuroendocrine markers (cNEM), such as synaptophysin, chromogranin-A, INSM1, and CD56/NCAM1. However, these tumors remain diagnostically challenging due to overlapping histologic and immunohistochemical features. The transcriptional regulators ASLC1, NEUROD1, POU2F3 and YAP1 are novel NEM (nNEM) used for subtyping of small-cell lung cancer (SCLC). Herein, we assessed the immunoexpression of nNEM in 76 sinonasal malignancies including 27 olfactory neuroblastomas (ONB), 14 small-cell (SCNEC) and 2 large-cell neuroendocrine carcinomas (LCNEC), 12 sinonasal undifferentiated carcinomas (SNUC), 7 olfactory carcinomas (OC), 11 SWI/SNF-deficient carcinomas, and 3 neuroendocrine tumors (NET). We correlated nNEM expression with the extent of neuroendocrine differentiation defined by averaged cNEM expression (NE-high: H-score≥150, NE-low: H-score<150). Dominant NE subtypes were defined by the nNEM with the highest H-score. Co-expression of two nNEM with <100 H-score difference defined a co-dominant NE subtype. NE differentiation positively correlated with NEUROD1 and negatively with YAP1 expression (p<0.0001). ONB were NE-high (96%) and all were NEUROD1-dominant/POU2F3-negative/ASCL1-negative(low)/YAP1-negative(low). In contrast to ONB, all OC were NE-low, mostly (71%) co-dominant subtypes, and NEUROD1-low(negative) (100%, p=0.0001) and YAP1-high (71%, p=0.0001). Most notably, all SNUC were POU2F3-(co)dominant/NEUROD1-negative irrespective of the IDH2 mutations. Sinonasal tumors with high POU2F3 expression showed enrichment for "tuft cell carcinoma" and tuft cell signatures (p=0.009). Similar to SCLC, SCNEC was heterogeneous in terms of nNEM expression comprising several molecular subtypes including ASCL1-(co)dominant (43%) cases. All SWI/SNF-deficient carcinomas were consistently ASLC1/NEUROD1/POU2F3-negative and YAP1-positive. ASLC1/NEUROD1/POU2F3/YAP1 are useful markers in differential diagnosis of ONB, SNUC, OC and SWI/SNF-deficient carcinomas. Subsets of SNUC and LCNEC may represent tuft cell-like carcinomas suggesting that the tuft cell could be explored as the cell of origin for these tumors. The therapeutic vulnerabilities associated with POU2F3 expression in SCLC suggest that a similar approach might be considered for POU2F3-positive carcinomas of the sinonasal tract. Given their diagnostic and possible therapeutic relevance, nNEM have potential to transform the way we approach the diagnosis and management of sinonasal small round epithelial/neuroepithelial malignancies., (Copyright © 2024. Published by Elsevier Inc.)