Tuesday 29 March 2005
Definition: Fibrofolliculoma is a very rare benign tumor of the skin that is derived from the perifollicular sheath. The patients with multiple fibrofolliculomas have an association with Birt-Hogg-Dube syndrome.
It is a neoplastic proliferation of the fibrous sheath of the hair follicle, with solid extensions of the epithelium of the follicular infundibulum.
As a benign tumor derived from the dermal part of a hair follicle, it may appear as a dome-shaped yellowish papule on the skin, accompanied by strands of follicular epithelium.
There is an expansion of the perifollicular sheath. The lesion consists of increased spindled fibroblast-like cells and a dense fibrous stroma. There is no atypia or mitotic activity.
Perifollicular fibroma, trichodiscoma, and fibrofolliculoma are similar entities, which may be variants of the same theme. Perifollicular fibroma is often used when the lesion resembles an angiofibroma or fibrous papule, as in this case. All of these lesions are derived from the perifollicular sheath, and thus contain a mesenchymal component.
When multiple, as in this case, there is an association with Birt-Hogg-Dube. These patients have a higher risk for renal cell carcinomas.
Fibrofolliculoma is a very rare benign tumor of the skin that is derived from the perifollicular sheath.
The tumor commonly presents as asymptomatic, multiple, small, white or flesh-colored, smooth, dome-shaped papules predominately over the scalp, face, oral cavity, neck, and upper trunk.
Fibrofolliculomas are 2 to 4mm in diameter, dome-shaped, yellowish or skin-colored papules usually located on the head, neck, and upper trunk.
Microscopically, the tumor shows a well-circumscribed dermal tumor with a central well-formed dilated hair follicle. The neoplastic epithelial cells form thin anastamosing cords that radiate from the central hair follicle. The perifollicular stroma is accentuated and fibrotic.
It shows a well-formed central hair follicle with a dilated infundibulum containing laminated keratin with anastomosing epithelial strands that radiate from the central hair follicle into the perifollicular fibrotic stroma.
Histologic sections of skin show a well-circumscribed lesion centered around a hair follicle. The perifollicular stroma is accentuated and fibrotic. Thin anastamosing cords of epithelium "wrap around" the lesion.
Predisposition and associations
Birt-Hogg-Dube syndrome (FLCN germline mutations)
Patients with multiple fibrofolliculomas have an association with Birt-Hogg-Dube syndrome (BHDS) that presents with cutaneous fibrofolliculomas, trichodiscomas, and acrochordons.
Trichodiscoma is a small hamartomatous tumor of the hair disk with a proliferation of the fibrovascular component of the hair disk and small melanin granule containing cells and occasional myelinated nerves. Perifollicular fibroma characteristically has a central hair follicle with hair shaft that is surrounded by circumferentially arranged fibrous sheath. Fibrofolliculoma, trichodiscoma, and perifollicular fibroma are closely related lesions. They may be the same entity and the different histologic appearances may be due to the plane of sectioning.
BHDS is also associated with renal tumors, particularly chromophobe renal carcinoma and renal oncocytoma, pulmonary cysts, spontaneous pneumothorax, colonic polyps, and colonic carcinoma.
Other associated features include large connective-tissue nevus, parathyroid adenomas, flecked chorioretinopathy, bullous emphysema, lipomas, angiolipomas, parotid oncocytomas, multiple oral mucosal papules, neural tissue tumors, and multiple facial angiofibromas.
BHDS has an autosomal dominant inheritance with a mutation on band 17p11.2 that involves a novel BHDS protein called folliculin.