Multiple Large Cysts Arising from Nevus

Nevus comedonicus is a type of hamartoma that arises from a developmental anomaly of themesodermal part of the pilosebaceous gland. In most cases of nevus comedonicus, an acnelikeskin condition develops. Repeated inflammation can cause a morphological change to thecyst, papule, to abscess. We experienced a case of congenital nevus comedonicus, which ledto the formation of large multiple cysts. A 50-year-old man was referred with a 12.5×10 cmlobulated mass on the posterior neck and upper back. The patient had a widespread presenceof nevus comedonicus in the region ranging from the right superior chest to the posteriorneck. The patient had a 30-year history of six prior excisions. A magnetic resonance imagingreview led to a diagnosis of nevus comedonicus. Surgical treatment consisted of excision ofthe mass and wide excision for the patch type of nevus comedonicus around the neck. Onhistopathology, multiple masses were diagnosed as typical cysts containing keratinized tissue.The diffuse comedone lesions were diagnosed as nevus comedonicus. This case shows thatlarge, multiple cysts can occur as a long-term complication of nevus comedonicus, and alsohighlights the importance of radical resection to prevent its further invagination.