Pilomatrix carcinoma with lymph node and pulmonary metastasis: report of a case arising on the knee.

A 58-year-old woman presented with a pilomatrix carcinoma on the right knee. The tumor developed at the site of a previous lesion that had been present since she was 30 years old. Histologic study showed the presence of basaloid cells with numerous atypical mitoses, shadow cells, and calcification.