Primary cutaneous B-cell lymphoma.

A 63-year-old woman presented with a single plaque on her left earlobe that was shown to be a B-cell lymphoma on histopathologic examination. Immunohistochemical studies on the paraffin-embedded tissue and flow cytometry of fresh tissue helped characterize the neoplasm. She had no other systemic involvement and a diagnosis of primary cutaneous B-cell lymphoma was made. This neoplasm has, in general, a good prognosis with excellent response to radiation therapy, polychemotherapy, or both.