Pseudohorn associated with basal cell carcinoma

Cutaneous horns usually represent compacted keratin arising from an underlying pathologic process and are important to dermatologists because they may indicate an underlying malignancy. The differential diagnosis of cutaneous horns includes pseudohorns, which have the morphologic appearance of a cutaneous horn but consist entirely of benign or malignant tumor. We describe a second type of pseudohorn consisting of hair, dried serum, and inflammatory exudate that was associated with an underlying basal cell carcinoma.