Primary Cutaneous Apocrine Carcinoma in an 82-Year-Old Male

Primary cutaneous apocrine carcinoma is a rare adnexal malignancy, often presenting a diagnostic challenge due to its resemblance to metastatic ductal carcinoma of breast. We report the case of an 82-year-old male with a painless, progressively enlarging swelling in the left axilla over a year. Clinical impression was a sebaceous cyst. Following an excision biopsy, histopathology demonstrated a well-circumscribed, unencapsulated neoplasm in the dermis with apocrine differentiation. The hallmark feature of decapitation secretion was observed. Immunohistochemical studies with GCDFP 15, CK7, ER, PR, HER2 and S100 antigen supported the diagnosis. The patient underwent complete excision and is doing fine without recurrence since January 2024. This case highlights the importance of meticulous morphological and immunohistochemical evaluation to distinguish primary cutaneous apocrine carcinoma from metastatic ductal carcinoma of breast.