Sweat gland carcinomas with nodular and basaloid differentiation

Abstract Sweat gland carcinomas pose a significant diagnostic challenge to histopathologists due to their rarity, their considerable morphological spectrum and their frequent resemblance to cutaneous metastases of visceral primaries. The behavior of sweat gland carcinomas ranges from indolent to aggressive with significant metastatic potential and mortality rates. Confident and correct diagnosis is therefore crucial to guide treatment and predict outcome. This review focuses on four sweat gland carcinomas, cutaneous cribriform carcinoma, endocrine mucin-producing sweat gland carcinoma, spiradenocarcinoma and aggressive digital papillary adenocarcinoma. These tumors show many overlapping histological features and are characterized by a lobular architecture and basaloid differentiation but vastly different clinical behavior. The article emphasizes subtle differentiating features, clinical and morphological clues and immunohistochemical expression patterns, and the key differential diagnoses are provided for each entity.