Sweat Gland Tumors: From Morphology to DNA?

Abstract

Skin adnexal tumors are a contentious aspect of skin pathology. They are rare, but a vast number of entities are reported in the literature. Because of the rarity of these tumors, categorization is often arbitrary and inconsistent. Literature is confusing and there are different conceptual views of individual observers which causes disagreement among expert pathologists. Skin adnexal tumors can traditionally be categorized by tumors with hair follicle, sebaceous and sweat gland differentiation. Classification of skin adnexal tumors is necessary for different reasons. This applies for sweat gland tumors as well. (1) Sweat gland tumors show a wide morphologic spectrum but malignant change is rare. Malignant sweat gland tumors are classified according to their behavior into low- and high-grade tumors. Low-grade malignant tumors are characterized by risk for locally destructive growth and local recurrence and but only rare distant metastasis, whereas high-grade tumors have significant metastatic potential and disease-related mortality. (2) Precise classification and accurate diagnosis is necessary to predict behavior of these tumors, which gives guidance for treating these tumors. (3) Recognition of sweat gland tumors associated with inherited tumor predisposition syndromes like Brooke-Spiegler is important for treatment, screening and genetic counseling. (4) Cutaneous metastases from visceral primary adenocarcinomas are important considerations in the differential diagnosis of sweat gland carcinomas, and reliable separation may be impossible on morphologic and immunohistochemical grounds. Clinical correlation therefore is highly important.