Nodular hidradenoma of breast skin mimicking metaplastic squamous carcinoma of the breast: A case report

Nodular hidradenoma is an uncommon benign skin tumor arising from sweat glands that most commonly present in the head and neck as an indolent protruding cutaneous nodule with external skin changes. More rarely, they may arise in the breast skin with characteristics that may mimic metaplastic carcinoma, resulting in a diagnostic dilemma for physicians. We report a case of breast skin nodular hidradenoma with an unusual presentation and initial concern for invasive metaplastic breast carcinoma on core-needle biopsy. We discuss the diagnostic challenges of this rare breast tumor with recommendations for future diagnostic strategies when concerned for skin-based breast lesions.