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Case Reports

Abstract

Primary cutaneous cribriform tumor (PCCT; previously carcinoma) is an underrecognized indolent adnexal neoplasm with apocrine ductal differentiation. Although small case series and reports have described its characteristic histologic appearance and immunohistochemistry findings, the molecular underpinnings of this rare tumor remain elusive. Here, we present on the comprehensive molecular profiling of a case of PCCT. A 55-year-old man presented with a 2 cm mass on his right back. Histologic examination revealed a circumscribed unencapsulated dermal tumor composed of interconnected epithelial cords and nests with a cribriform pattern including numerous dilated cystic spaces, invested in a densely hyalinized, desmoplastic stroma. Intraluminal eosinophilic secretions and occasional small micropapillae were observed, and lymphoid aggregates surrounded the tumor. Immunohistochemical analysis revealed variable expression of CK5, CK7, CEA (luminal), SOX10, and S100 and a lack of expression of p63, p40, CK20, TTF1, and CDX2. Comprehensive molecular profiling revealed a low tumor mutational burden and identified a likely pathogenic missense mutation (p.R1830H) at exon 38 of the neurofibromatosis 1 (NF1) gene. Copy number analysis by whole exome sequencing revealed homozygous loss of chromosomes 6q and 9q and several additional smaller gains and losses. No in-frame gene fusions were detected. This case sheds new insights into the molecular pathogenesis of PCCT. Molecular analysis of additional cases is currently underway.