Case 20 - Discussion
Uploaded: 2007-09-27, Updated:
uncommon hamartoma of hair follicle tissue, typically occurring
in the head and neck of adults. Represent
abortive differentiation of pluripotent skin cells toward hair
associated with systemic disease or other skin disorders. The
prognosis is excellent, and therapy is usually directed toward
Gross: Non-specific flesh-colored
nodule, often with a central keratinous plug containing vellus
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.
trichofolliculoma, similar histologic features, except for the
presence of numerous well-differentiated sebaceous lobules
emptying into the central, dilated primary follicle.