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Case Reports

Abstract

Nevus sebaceus (of Jadassohn), also known as organoid nevus, is a complex congenital hamartoma of epidermis and adnexal structures, composed of an overgrowth of epidermis, sebaceous glands, hair follicles, apocrine glands, and connective tissue. Affecting approximately 0.3% of newborns, organoid nevi are generally present at birth or in early childhood. While these lesions were previously thought to have a high risk of developing secondary malignancies, current research has shown that this risk is low, estimated at less than 1%. Microscopically, nevus sebaceus is characterized by abundant mature sebaceous glands, immature hair follicles and papillomatous epidermal hyperplasia. Generally, these lesions show mutations in the RAS pathway, most commonly HRAS and rarely KRAS. Common associated secondary tumors in adults are trichoblastoma, syringocystadenoma papilliferum and hidradenoma. Interestingly, many of these lesions share similar RAS mutations to the initial nevus sebaceus. Herein we present a 65-year-old female patient who presented to a dermatology clinic with a yellow plaque with blue and erythematous nodules on her forehead. A broad shave was taken which showed histomorphologic features consistent with a nevus sebaceus. Interestingly, within a background of the nevus sebaceus, four secondary tumors had developed including a trichoblastoma, sebaceoma, apocrine hidradenoma and an apocrine cystadenoma.  While there are reports of multiple secondary adnexal neoplasms arising from nevus sebaceus, the presence of four simultaneous secondary tumors in this hamartoma is quite rare and suggests the necessity of excising these lesions early.