Pilomatricoma with a bullous appearance.

A 15-year-old Japanese girl had an asymptomatic nodule on the right thigh of seven months' duration. The clinical appearance was similar to that of a bulla. There was a history of blunt trauma from dog scratch to the skin over the tumor shortly before tumor growth. Histopathological findings were consistent with pilomatricoma. In the overlying dermis, the collagen bundles were compressed to the tissue surrounding the tumor and the large space was seen. Around the tumor, some dilated endothelium-lined vascular channels were found, which were identified as lymphatic vessels.