Cutaneous ultrasound: key diagnostic tool for the relapse of a single eccrine spiradenoma.

Eccrine spiradenoma is a rare, benign, adnexal skin tumor of the sweat gland. It is frequently solitary and presents as a small lesion in the dermal or the subcutaneous fat layer. Eccrine spiradenomas rarely progress to malignant transformation but they can relapse. Due to its rarity, there have been few reports about the sonographic appearances of eccrine spiradenoma. Sonographic findings were reported in a relapsing case of an eccrine spiradenoma, located in the deep dermal layers and hypodermis of the preauricular region in a middle-aged man. Ultrasound was very useful to suspect the relapse. Histology was correlated with the sonography and discussed the previously reported imaging findings of eccrine spiradenoma and other sweat gland tumors.