Case 20 - Discussion

Uploaded: 2007-09-27, Updated: 2007-12-01

Trichofolliculoma

• An uncommon hamartoma of hair follicle tissue, typically occurring in the head and neck of adults. Represent abortive differentiation of pluripotent skin cells toward hair follicles.

• Not associated with systemic disease or other skin disorders. The prognosis is excellent, and therapy is usually directed toward cosmetic improvement.

• Gross: Non-specific flesh-colored nodule, often with a central keratinous plug containing vellus hairs.

• Histology: classic trichofolliculoma has a central pore that consists of a dilated primary follicle lined by infundibular/isthmis, stratified squamous epithelium with opening to the skin surface. Numerous secondary and tertiary follicles bud from the "parent" in a centrifugal fashion, presenting at various levels of hair-follicle differentiation. Hair structures may be observed within the hair follicle lumen; small sebaceous elements may be found within the follicular units. Minimal lymphocytic or granulomatous inflammation may be present. An abundant connective tissue stroma is also present surrounding the follicular structures.

• Abundant Merkel cells have been demonstrated within the follicular epithelium, supporting the concept that trichofolliculomas are hamartomas.

• Variant: sebaceous trichofolliculoma, similar histologic features, except for the presence of numerous well-differentiated sebaceous lobules emptying into the central, dilated primary follicle.

Reference

• AFIP, nonmelanocytic tumors of the skin, series 4

• http://www.emedicine.com/derm/topic546.htm