Primary cutaneous apocrine carcinoma with RARA::NPEPPS fusion

• DOI: 10.1111/cup.14607
• Publication Date: 2024-03-12T07:25:10Z
• Authors: Volha Lenskaya; Richard K. Yang; Woo Cheal Cho
• Keywords: PAX8; Apocrine

Gene fusions have emerged as crucial molecular drivers of oncogenesis in a subset cutaneous adnexal neoplasms, including poroid neoplasms and hidradenomas. We present unique case primary apocrine carcinoma harboring RARA::NPEPPS fusion, broadening the spectrum fusion-associated neoplasms. A 77-year-old African American male presented with an ulcerated thigh nodule. Histopathologically, predominantly dermal-based adenocarcinoma exhibited papillary, micropapillary, cribriform, solid growth patterns central comedonecrosis, set fibrotic/desmoplastic stroma. Immunophenotypically, neoplastic cells were positive for CK7, CK19, GATA3, TRPS1, HER2, CK5/6, calretinin, p63, DPC4 (no loss), while lacking immunoreactivity CK20, CDX2, TTF1, napsin-A, PAX8, arginase-1, adipophilin, NKX3.1, uroplakin II, D2-40. The immunoprofile clinical radiographic absence any internal malignancy, breast carcinoma, except multiple lymphadenopathy, supported diagnosis carcinoma. Next-generation sequencing unveiled novel concurrent ERBB2 amplification, somatic mutations involving TP53, CDKN2A, BRCA2, PIK3CA, PIK3R1, others. patient developed widespread metastases within year after initial diagnosis, indicating tumor's aggressive behavior. This unprecedented human malignancies carcinomas, may suggest potential new subtype