We performed a clinicopathological study of secondary neoplasms involving 243 cases of nevus sebaceous. Secondary neoplasms were observed in 33 cases (13.6%). The 43 lesions included 33 lesions of benign neoplasms and 10 malignant neoplasms were also observed in those 33 cases. The cases with secondary neoplasms increased in number after puberty, and, in 11 out of 21 cases (52.4%) who were more than 50 years old, secondary neoplasms were observed. Malignant neoplasms were seen only in cases more than 30 years old. Secondary neoplasms were most frequently observed in cases with lesions on the face. We compared the histopathological findings between the cases with and without secondary neoplasms. There were no statistically significant differences between these two categories other than an association with independent sebaceous glands. We compared these findings with formerly reported ones in Japan and foreign countries. Although the incidence of secondary neoplasms was almost equal to that in other reports in Japan, it was lower than that in foreign countries. The incidence of malignant neoplasms was as low as that reported in reports from foreign countries. Based upon these findings, we recommend that resection of a nevus sebaceus should be perfomed for esthetic reasons in cases before young adulthood, and also when any tumor is associated, with the nevus in cases over 30 years old.
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