Simultaneous occurrence of two squamous cell carcinomas developing in a nevus sebaceous.

Nevus sebaceous (NS), also known as organoid nevus, is a congenital skin hamartoma involving pilosebaceous follicle, epidermis and adnexal structures, which usually occurs in the head and neck region. During the first stage, which is seen in infancy and childhood, the lesion remains static, but can subsequently grow during puberty to become more evident and verrucous or nodular. Depending on the location and extent, nevus sebaceous causes only a cosmetic problem during childhood; however, the development of benign and malignant neoplasms on the lesion is the most severe complication during adulthood. The association between nevus sebaceous and various benign and malignant cutaneous neoplasms is well documented. Basal cell carcinoma (BCC) is the most common malignant lesion, and syringocystadenoma papilliferum (SP) is the most common benign tumor associated with nevus sebaceous. Development of squamous cell carcinoma within NS is very rare. The literature contains only a few reports of simultaneous multiple malignant tumors developing on nevus sebaceous. We present a review of the literature and report the case of a 42-year-old female patient with two squamous-cell carcinomas (SCC) simultaneously within a single NS.