FIBROFOLLICULOMA
Fibrofolliculomas
are uncommon benign tumors of the skin. They are derived from the hair follicle
epithelium and show a unique mantle differentiation. These tumors are
uncommonly seen, but if they are seen in multiples, one needs to consider that
they are a constellation of Birt-Hogg-Dubé syndrome.
Clinical Findings: These tumors, when seen, are often
solitary skin growths on the head and neck. They are small (2-5 mm),
flesh-colored to tan-yellow papules. They most commonly manifest in the third
or fourth decade of life. They are asymptomatic and rarely, if ever, get
inflamed or bleed spontaneously. On occasion, a small hair is seen emanating
from the center of the lesion. The main differential diagnosis clinically
includes compound nevus, basal cell carcinoma, fibrous papule, and other types
of adnexal tumor. Definitive diagnosis is impossible without histological
examination. Solitary fibrofolliculomas are usually found incidentally on
routine skin examination. Some patients present with a slightly enlarging new
papule, often expressing concern for or fear of skin cancer.
Multiple fibrofolliculomas are seen in association with Birt-Hogg-Dubé
syndrome. This syndrome is caused by a genetic defect in the tumor suppressor
gene, folliculin (FLCN). This gene has been localized to the short arm
of chromosome 17. Other cutaneous constellations of this autosomal dominantly
inherited syndrome include trichodiscomas and skin tags. The most important
aspect of diagnosing this syndrome early is to screen patients for the
possibility of renal tumors, both benign and malignant. Renal oncocytomas are
the most common malignant renal tumor seen in this syndrome. Another rare renal
cancer, the chromophobe renal cell carcinoma, also may be seen. This very rare
tumor is seen in a higher percentage of patients with Birt-Hogg-Dubé syndrome
than in the general population. It has a less aggressive behavior than other
forms of renal cell carcinoma. Patients with this syndrome are also at higher
risk for spontaneous pneumothorax. Some believe that trichodiscomas are the
same type of tumor as the fibrofolliculoma and that the difference in
histological appearance is caused by sampling and pro- cessing artifact (i.e.,
the identical tumor processed at different tissue surface levels).
Pathogenesis: Fibrofolliculomas are believed to be derived from the upper part of the
follicular epithelium. The tumors are thought to be hamartomatous processes
that develop within the dermis. Mantle-like structures, as seen in sebaceous
glands, are often present and may be the derivation of these tumors. Some
authors even consider the manteloma (an extremely rare benign skin tumor) to be
in the same spectrum of tumors as the fibrofolliculoma and the trichodiscoma.
Histology: The tumor surrounds a well-formed terminal hair
shaft. The upper portion of the hair shaft is slightly dilated. Emanating from
the central hair shaft epithelium are
cords or epithelial strands that project into the surrounding dermis. These
cords interconnect at various positions and form a weave-like pattern.
Trichodiscomas do not contain a hair shaft; one sees a proliferation along a
hair follicle of a fibrovascular stroma akin to an angiofibroma. It is
postulated that these two tumors are indeed the same but appear to be two
distinct tumors due to routine processing and sampling at various tissue plane
levels.
Treatment: Solitary fibrofolliculomas can be removed
completely with the shave removal technique. This gives excellent cosmetic
results, and the tumors are unlikely to recur. Multiple tumors are more difficult
to remove; laser resurfacing, dermabrasion, and chemical peeling have all been
used with varying results. The recognition of multiple fibrofolliculomas or
trichodiscomas nec ssitates screening for Birt Hogg-Dubé syndrome.
