Abstract

Basal cell carcinoma (BCC) is the commonest malignancy often occurring superficially in the skin and rarely metastasizing or involving underlying bone. The different histomorphologic manifestations of BCC and other factors often contribute to the behavior and clinical course of the disease. We report the case of a 72-year-old man who presented with multiple flesh-colored papules or nodules on the skin of the face, chest, and back that had been present for several years. The largest was a 6.5 cm ulcerated mass that grossly appeared to involve the underlying zygomatic arch. He underwent extensive facial surgery and reconstruction involving resection of the right facial skin, nerve, zygomatic arch, and parotid gland. Histologic examination revealed a predominantly dermal-based lesion with overlying epidermal ulceration. The basaloid tumor cells display varying morphology including nodules, nests, and infiltrative cords with extensive necrosis and invasion of the underlying skeletal muscle and bone. The tumor extensively involved the bone marrow of the zygomatic arch with histologic patterns reminiscent of ameloblastoma, adamantinoma, and adenoid cystic carcinoma. Although BCCs are known to be locally aggressive, cases with bone involvement are rarely reported in the literature. Some of these reported cases are recurrent lesions or metastasis to the bone by hematogenous spread. Our case of a primary BCC with extensive bone marrow invasion uniquely illustrates potential histologic mimics that may be confounding in recurrent or metastatic lesions.

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