A 24‐year‐old man was admitted to our outpatient clinic with lesions in a linear configuration. On dermatologic examination, widespread, dark brown, warty papules and plaques over an erythematous base, following Blaschko"s lines, extended from the middle of the chest to the right arm. These lesions had been present on the chest since birth and had gradually extended during childhood. Recently, a nodular lesion had appeared in the pre‐existing epidermal nevus in the middle part of the chest (Fig. 1). The nodular lesion was totally excised by a plastic surgeon.
Basal cell carcinoma (white arrow) appearing on the epidermal nevus in the middle part of the chest
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Pathologic examination of a section stained with hematoxylin and eosin revealed acanthosis and papillomatosis, as well as numerous sebaceous glands connected to the epidermis (Fig. 2). This histologic feature was compatible with nevus sebaceous. In addition, in the middle of the section, there was a tumor connected to the epidermis. Histologically, the tumor islands, composed of basaloid cells with mostly solid growth pattern, were compatible with basal cell carcinoma. There were also some features of nevus sebaceous, characterized by papillomatosis, and sebaceous glands attached to the epidermis were seen at the edge (Fig. 3).
Acanthosis and papillomatosis, as well as numerous sebaceous glands connected to the epidermis (hematoxylin and eosin stain; original magnification, × 40)
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Basal cell carcinoma characterized by tumor islands composed of basaloid cells, and a component of nevus sebaceous, the sebaceous glands being attached to the epidermis (hematoxylin and eosin stain; original magnification, × 40)
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On systemic examination, there was no other developmental abnormality, except that the patient was mildly mentally retarded. There was no family history of a neurocutaneous disorder. All laboratory analyses were within normal limits.