Update on Malignant Sweat Gland Tumors.

Malignant sweat gland tumors are rare cutaneous neoplasms, traditionally separated according to their behavior into low- and high-grade malignant. There is significant morphologic overlap, and outright malignant tumors may show relatively bland histologic features. They may, therefore, be mistaken easily for benign neoplasms. Recognition of these tumors and accurate diagnosis is important for early treatment to prevent aggressive behavior and adverse outcome. This article provides an overview of 4 important entities with emphasis on diagnostic pitfalls, differential diagnosis and recent developments. Microcystic adnexal carcinoma, squamoid eccrine ductal carcinoma, aggressive digital papillary adenocarcinoma, and spiradenocarcinoma are discussed in detail.