Pilomatrix carcinoma

A rare skin tumor characterized by an asymptomatic, solitary, often ulcerated nodule most commonly located in the face, involving the deep dermis, subcutaneous tissue, and skeletal muscle and fascia. Histopathologically, the lesion is composed of aggregates of atypical basaloid cells with numerous mitoses. Typical features include shadow cells, keratin cysts, and trichohyalin and keratohyalin granules. The tumor is locally aggressive and shows a tendency to recur after incomplete excision. Regional lymph node or visceral metastasis has been reported.