Sebaceous trichofolliculoma.

Sebaceous trichofolliculoma, a hitherto unrecognized variant of trichofolliculoma, is a clinically and histologically easily recognizable tumor of higher than usual differentiation. Clinical features, histology, differential diagnosis and therapy are presented, using as a basis three patients (all male, ages 21, 36, and 51). Clinically, sebaceous trichofolliculomas occur in sebaceous follicle-rich areas (in all three cases here, the nose). They are skin-colored, centrally depressed lesions of 4--12 mm in diameter. Lateral borders and depth of hamartoma cannot be sharply delineated. Thick terminal hairs, vellus-hairs and occasional trichoids protrude from a fistula-like opening. No connecting tract to paranasal sinus and no bony destruction were found using radiopaque techniques. Histologically, the sebaceous trichofolliculoma has a characteristic pattern. It is a hamartomatous growth, with a rather large central cavity or sinus and with secondary branches, all keratinizing. The cavity is filled with loose epidermoid corneocytes, trichilemmal-like cellular debris, and hairs. Many strikingly large sebaceous follicles (unlike the picture in sebaceous ducts, follicular infundibula, and hair-follicle units. Terminal hair-follicles and vellus hair-follicles are found in various stages of the hair growth-cycle. There is usually no inflammation. Differential clinical diagnosis includes dermoid cysts and congenital fistulas (which may have widespread cords, sacs or ducts to the paranasal structures). Histological differentiation should include trichofolliculoma, pilar sheath acanthoma, dilated pore, circumscribed sebaceous gland hyperplasia, and steatocystoma multiplex. Therapy consists of surgical excision.