A 59-year-old Japanese male had a solitary tumor on the thigh for 3 years. Histopathology of the tumor showed nodular and reticulated patterns of proliferation of basaloid cells and cords of squamoid cells throughout the entire dermis. In the center of the tumor, dilatation of a hair follicle and numerous infundibular cysts were noted. Some hints of differentiation to dermal papilla were noted. These histopathologic features were considered to be compatible with the diagnosis of infundibulo-cystic basal cell carcinoma. Unusual site and rather deep invasion of the tumor suggest that infundibulo-cystic basal cell carcinoma may be one type of true malignant skin tumor but not a benign tumor.