Immunohistochemical characterization of pleomorphic giant cells in basal cell carcinoma.

Over 20 cases of basal cell carcinomas with pleomorphic giant cells of the mononuclear or multinucleate type have been described. The nature of these cellular and nuclear changes has not been elucidated. Some authors found that these cells have phagocytic properties and others reported an aneuploid DNA content. We have seen mitotic figures in some of these giant cells, and postulate that these cells are capable of proliferation. Twelve cases of basal cell carcinoma with pleomorphic giant cells were examined using monoclonal antibodies recognizing the proliferating cell nuclear antigen (PCNA), Ki-67, and bcl-2 antigens. Expression of proliferation associated antigens in the giant cell population was higher than in the small cell population. Over expression of bcl-2 was detected in both the small and giant cells in all cases. The results demonstrate that the giant tumor cells are cycling and express bcl-2 protein in a manner consistent with basal cell carcinoma. The changes are unlikely to represent a senescent change as seen occasionally in mesenchymal neoplasms.