Fibroepithelioma of Pinkus: eccrine duct spread of basal cell carcinoma

The spread of basal cell carcinoma (BCC) directly into the dermis or down the sides of hair follicles is a common-place pathologic observation. BCC spread via eccrine ducts, which has received less recognition, is the subject of this investigation. We specifically address the question of whether eccrine duct spread accounts for the histologic pattern of the fibroepithelioma of Pinkus (feP) type of BCC. Twenty-five BCC, including 12 feP, five superficial BCC, six ordinary BCC, one BCC of the sole of the foot, and one BCC with prominent hair follicle spread were studied with H&E sections; 11 were immunostained for carcinoembryonic antigen. In ordinary BCC, occasional entrapped eccrine ducts were present. One superficial BCC surrounded the proximal portion of an eccrine duct. The BCC from the sole of the foot showed advanced spread down eccrine ducts; focal obliteration of duct epithelium and lumen was seen, as was transition to strands of solid BCC. Nine of the 12 feP showed one or several eccrine duct foci with tumor strands. These findings suggest that eccrine ducts serve as an initial template in feP and subsequently are replaced by the BCC. However, eccrine duct spread of BCC may occur without necessarily imparting an feP histologic pattern.