Clear Cell Differentiation in Eccrine Porocarcinoma as a High-Risk Feature: Epidemiologic and Pathologic Features of Eccrine Porocarcinoma in a Single-Center Case Series.

Eccrine porocarcinoma (EPC) is a rare sweat gland malignancy. Recognition of histologic features is challenging, and specific pathologic features correlate with risk of poor outcome. This single-center retrospective review and case series of 58 EPC cases from 2000 to 2016 elucidates epidemiologic and pathologic characteristics of EPC. Pathology slides from 52 cases were analyzed by a dermatopathologist for standardized variable characteristics, including previously determined high-risk features (HRF) associated with poor prognosis. The incidence of EPC increased over the study period with 3 times more cases diagnosed in the last 4 years than in the first 4 years. Most cases were in the elderly males (mean age 75 years), and 50% were located in the head and neck region. Although 38% of tumors exhibited one histologic HRF, only 10% exhibited more than one. Of the HRF, a greater tumor depth was associated with both increased age (P = 0.04) and clear cell differentiation (P = 0.02). This study elucidates epidemiologic and pathologic features of EPC and highlights how age and clear cell differentiation can be associated with greater tumor depth, although further research is needed to determine whether clear cell differentiation is associated with poor clinical outcome.