This lesion on the scalp of a 78-year-old man was clinically thought to be a squamous cell carcinoma. Syringocystadenoma papilliferum is a rare lesion, often found on the scalp, but can occur more rarely at other sites. They are often associated with a nevus, such as nevus sebaceus. Although these lesions may be flat, it is not uncommon for them to have a warty appearance, as in this case. Usually, one will find continuity of the cyst with the overlying epidermis, although this was not found in our case. They behave in a benign fashion.
Histologic sections of skin show a cystic lesion subjacent to an acanthotic epidermis. The lesion has islands, or bulbous papillary projections, filled with basophilic cells, and lined by plump epithelial cells. The cystic spaces appear clear.