2013 Volume 75 Issue 2 Pages 141-144
A 64-year-old female presented with comedo-like lesions from the right shoulder to the cervix that had been present since early childhood. These lesions showed a linear and Z-like arrangement and were characterized by multiple scars and comedones of various sizes. She underwent excision three times, and the lesions were diagnosed clinically as nevus comedonicus. Microscopic examination revealed irregular funnel-, spindle-, and glove-shaped recesses in the epidermis and also showed epidermal cyst-like structures filled with stratified keratin. In addition, in a part of the cystic structures the microscopic characteristic findings in the present case were as follows: 1) the cystic wall accompanied mature sebaceous glands, 2) vellus hairs were present, 3) by immunohistochemistry, almost all cystic walls were positive for cytokeratin (CK) 1, which generally indicates positivity for epidermal infundibular hair follicle, whereas a part of the cystic walls presenting at dermis was positive for CK17, which usually expresses the differentiation between the hair follicle infundibulum and the hair bulb. The present case was diagnosed as nevus comedonicus, which might be hamartoma with differentiation of folliculosebaceous glands. Although the histogenesis of nevus comedonicus is unclear, the present case may be a key that can contribute to elucidatingthe histogenesis of this disease.
