Nevus sebaceus of Jadassohn is a complex anomaly involving the epidermis, dermis, apocrine glands and hair follicles, as well as the sebaceous glands, and a variety of benign and malignant tumors and neurologic abnormalities may be associated with it; however, only a few studies on it have been reported in the Korean literature.

The objectives of this study was to document clinical and histopathologic features of nevus sebaceus in Koreans and compare them to those in the previously reported studies.

Clinical records and histopathology of 53 cases of nevus sebaceus diagnosed at Ewha Womans University Tongdaemun Hospital during a period of 18 years were reviewed and analyzed.

The average incidence rate of nevus sebaceus among new patients was 0.03%. The male-to-female ratio was 1.04 and the average age at visit, 16.5 years. The lesions had been present since birth or had developed before age 10 in 85% of the cases. A11 lesions were situated on the head, and the most common site was the scalp. Linear 1esions (20.8%) were mostly facial lesions. Histopathologically, the incidence of sebaceous and apocrine glandular hyperplasia was most notable in the 13-18 and over-18 age groups. The sebaceous glands showed small punched out defects or "holes" in 24.5%; ectopic apocrine glands were found in 24.5 %. Mature hair follicles were absent or greatly reduced in number in 75.5%. Acanthosis nigricanslike pattern of acanthosis and mild papillomatosis were the dominant changes in the epidermis. Hyperplasias and neoplasms were associated in 15.1%, which included 5 cases of primitive follicular induction and 1 trichoblastoma.

In this series, no examples of malignant neoplasms were identified; however, an early total excision before age 13 is recommended since a variable "deficit malformation" of the follicles with hyperplasia of the epidermis and sebaceous glands becomes more prominent after that age.