Pilomatrical carcinosarcoma of the temple: A case report.

Pilomatrical carcinosarcoma is a very rare entity, with only six cases reported until now. This report describes the case of a 100-year-old woman with a mass on the left temple that had existed for several decades but had recently grown in size. Histology showed an asymmetric lesion composed of basaloid cells, spindle cells, and "shadow" or "ghost" cells. Cells had atypical hyperchromatic nuclei with prominent nucleoli, high mitotic activity, and atypical mitosis. In the central area, an epidermal cyst-like structure was seen. The diagnosis of pilomatrical carcinosarcoma was rendered. This case appeared to have arisen from malignant transformation of a pilomatricoma because of the long clinical history and existence of a benign epidermal cyst-like structure. In addition, the observation that the basaloid cells and spindle cells showed a gradual transition from one to the other and that both types were positive for β-catenin would seem to support a common clonal origin for the carcinomatous and sarcomatous components.