Bluish pigmentation of the gingiva in a homeless patient: a quiz. Burton's line revealing chronic lead poisoning (plumbism).

A 57-year-old Japanese man presented with a 10-year history of a plaque on his face. The lesion had gradually increased in volume. Physical examination revealed a brownish-grey plaque, approximately 5 x 5 cm in size, with ulcération on the right nasolabial area (Fig. la). Dermoscopy showed a milky-red area with some milia-like cysts and dilated vessels on the surface (not shown). Histopathological examination revealed a poorly circumscribed tumour invading deeply into the dermis and subcutis. Tumour nests composed of atypical basaloid cells were embedded in a desmoplastic stroma. Some keratinous cysts and cystic glands were seen in the mid-dermis. Small ductal or glandular structures were also seen in the deep dermis (Fig. 1 b, c). Immunohistochemically, most of tumour cells were positive for carcinoembryonic antigen (CEA).