The clinical differential diagnosis included cylindroma and pigmented basal cell carcinoma. The biopsy specimen showed large nodular aggregates of basaloid cells with peripheral palisading and abundant melanin. At the periphery, some basaloid cells appeared to recapitulate primitive follicular germs (Figure 4). There was no epidermal attachment. The nodules were surrounded by a fibrous connective tissue stroma in which occasional clefts were seen. Rare mitotic figures were present.
Asymptomatic Scalp Nodule Present for 20 Years. Arch Dermatol. 1999;135(6):707-c-712. doi:10-1001/pubs.Arch Dermatol.-ISSN-0003-987x-135-6-dof0699