Trichostasis spinulosa within an intradermal melanocytic nevus.

A thirty-six-year-old man presented with a melanocytic nevus on his left shoulder. The lesion was excised and histopathologic examination showed an intradermal nevus with several infundibular cysts among the nevus cells. These cysts showed a cyst wall with epidermoid keratinization and a lumen filled by many cross-sectioned hair shafts. These findings were consistent with a diagnosis of trichostasis spinulosa within an intradermal melanocytic nevus. We note the relationship between these two disorders in the same lesion.