Basal cell carcinoma with hyaline inclusions.

A 67-year-old woman had a basal cell carcinoma of the forehead containing numerous hyaline cytoplasmic inclusions. Electron microscopic studies revealed that these inclusions were aggregates of cytoplasmic filaments. Immunohistochemical studies demonstrated reactivity for keratin, vimentin, and smooth-muscle myosin in these structures. Because of potential diagnostic difficulties, the pathologist should be aware of this unusual form of basal cell carcinoma.