Clear Cell Hidradenoma and Hidradenocarcinoma Arising from Benign Hidradenoma: Imaging Findings of Ultrasonography and CT

ABSTRACT

Clear cell hidradenoma (HA) is a rare tumor of sweat glands. Although this tumor is benign, local recurrence often occurs when the resection margin is insufficiently obtained. The common imaging finding of HA is a mixed solid and cystic mass with or without increased vascularity in the solid portion. Malignant transformation of the tumor is also recognized. Hidradenocarcinoma (HAC), which is a malignant counterpart of benign HA, can develop de novo or arise from benign HA. However, imaging findings of HAC are not well established because these tumors are rare and they are commonly excised without imaging study. We present two cases of benign HA and HAC arising from benign HA with characteristic ultrasonography and computed tomography imaging features.