Nevus sebaceous (NS) is a benign hamartomatous lesion; however, benign proliferative lesions are less frequently associated with secondary neoplasms. The aim of this study is to evaluate the prevalence of secondary benign and malignant tumours seen in NS lesions, and to reveal the histopathological features of these lesions.
Eighty-six NS cases were retrospectively evaluated for gender, age, lesion location, and accompanying lesions, as well as secondary benign and malignant tumours. The data obtained using descriptive statistics were analysed.
66.3% of cases were male, 33.7% were female, and the mean age was 37.8 years. 61.6% of lesions were localised on the face, 37.2% on the scalp, and 1.2% on the back. Secondary lesion development was observed in 39.5% of cases. The most common malignancy, as reported in the literature, was basal cell carcinoma. 
Although secondary lesions, secondary tumours, and malignancy development are rare in NS lesions, careful follow-up and surgical excision if necessary are recommended, especially in adulthood. This study contributes to the literature by revealing the pathological characteristics of secondary lesions accompanying NS, emphasising the need for careful histological evaluation of NS excisions in the differential diagnosis and raising awareness that malignancies may be present.