Low-Grade and Intermediate-Grade Apocrine Intraductal Carcinoma Arising in a Nevus Sebaceous of Jadassohn.

Nevus sebaceous (NS) is a congenital hamartoma that may give rise to a wide spectrum of benign and malignant adnexal neoplasms, although malignant transformation is uncommon. We report a case of low- and intermediate-grade apocrine intraductal carcinoma arising in a NS of Jadassohn in a 93-year-old woman. Histopathologic examination demonstrated an intraductal apocrine neoplasm with solid and cribriform architecture, focal comedonecrosis, and an intact surrounding myoepithelial cell layer highlighted by p63 and CK5/6 immunostaining. The neoplastic cells expressed CK7, epithelial membrane antigen (EMA), and androgen receptor, whereas estrogen receptor, progesterone receptor, and HER2 were negative. The lesion was associated with basal cell carcinoma, trichoblastoma, and apocrine hidrocystoma within the same NS. The morphologic and immunophenotypic findings closely parallel those of mammary apocrine ductal carcinoma in situ, supporting the concept that analogous neoplastic transformation may occur in cutaneous apocrine ducts. This case expands the spectrum of malignant neoplasms arising in NS and contributes to the limited literature on this exceptionally rare entity. Gemini ha dicho.