‘ Real-Time ’ Observation during Pre-operative Workup of Malignant Transformation in Nevus Sebaceous

Abstract

　　It is well known that malignant neoplasms, particularly basal cell carcinoma, can arise within nevus sebaceous lesions. However, it is rare to observe such transformation in a short period of time. Here, we report a case of nevus sebaceous that developed malignancy during pre-operative observation. A 44-year-old Japanese woman with a congenital skin lesion on the left temporal region presented to our hospital for treatment. The lesion was diagnosed as nevus sebaceous from clinical findings, and surgical resection was scheduled. At the time of the first visit, there was no evidence of malignancy. However, 4 months after the first visit, a glossy, round and black nodule（2 mm in diameter）was found within the lesion. Subsequently, surgery was performed. Postsurgical pathological examination revealed malignant basal cells in the hyperplastic sebaceous glands, and the diagnosis was basal cell carcinoma in nevus sebaceous. Although it has been reported that most basal cell carcinomas grow slowly, this case suggests that once malignant transformation occurs in nevus sebaceous, the growth rate is much faster than previously believed. Therefore, careful observation is necessary when treating patients with nevus sebaceous.