A pedunculated follicular hamartoma: a case showing a central trichofolliculoma-like tumor with multiple trichogenic tumors.

We report a rare case with a pedunculated nodule on the nasal septum, which seems a kind of follicular hamartoma with a pedunculated appearance. Our case was a 77-year-old Japanese male with an 11 x 11 x 10 mm sized, skin-to-pink colored, pedunculated nodule on the center of his nasal septum. Histopathological study revealed the nodule to be a well-formed dilated hair follicle at the central pore of the tumor, where keratin debris and vellus hairs were present. In addition, epithelial cells forming long thin strands or immature follicle-like structures had proliferated multifocally from the epidermis of the wall of the central follicle to the peripheral epidermis. One distinctive feature was the formation of a primary germinal bud with thick concentric collagen fibers and sparse elastic fibers. Although a combined tumor of trichofolliculoma with highly-graded desmoplasia, multiple trichogenic trichoblastomas, and perifollicular fibromas was suggested, calling it a pedunculated follicular hamartoma seemed more useful because the pathological features were basically similar to reported follicular hamartomas and the clinical feature was so distinctive.