Page 38 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 2-11 Integumentary System

Fibrofolliculomas. Note the periauricular
and retroauricular location of monomorphous
papules. They are most commonly seen in
association with Birt-Hogg-Dubé syndrome.
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 Skin Finding in Birt-Hogg-Dubé
are uncommonly seen, but if they are seen in multiples,
one needs to consider that they are a constellation of 1. Fibrofolliculomas
Birt-Hogg-Dubé syndrome. 2. Skin tags
Clinical Findings: These tumors, when seen, are 3. Trichodiscomas
often solitary skin growths on the head and neck. They 4. Lipomas
are small (2-5 mm), flesh-colored to tan-yellow papules. 5. Angiolipomas
They most commonly manifest in the third or fourth 6. Angiofibromas
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 examina-
tion. Solitary fibrofolliculomas are usually found inci-
dentally 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 con-
stellations of this autosomal dominantly inherited syn-
drome 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 syn-
drome. 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 popula-
tion. 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- Low power. The tumor is made up of a centrally High power. Close-up view shows the basophilic
cessing artifact (i.e., the identical tumor processed at located basophilic tumor lobule with what appears tumor lobule and the fine hair shaft with keratin
different tissue surface levels). to be a hair shaft forming within the lobule. debris.
Pathogenesis: Fibrofolliculomas are believed to be
derived from the upper part of the follicular epithelium.
The tumors are thought to be hamartomatous pro-
cesses that develop within the dermis. Mantle-like epithelium are cords or epithelial strands that project Treatment: Solitary fibrofolliculomas can be
structures, as seen in sebaceous glands, are often present into the surrounding dermis. These cords interconnect removed completely with the shave removal technique.
and may be the derivation of these tumors. Some at various positions and form a weave-like pattern. This gives excellent cosmetic results, and the tumors
authors even consider the manteloma (an extremely Trichodiscomas do not contain a hair shaft; one sees a are unlikely to recur. Multiple tumors are more dif-
rare benign skin tumor) to be in the same spectrum of proliferation along a hair follicle of a fibrovascular ficult to remove; laser resurfacing, dermabrasion, and
tumors as the fibrofolliculoma and the trichodiscoma. stroma akin to an angiofibroma. It is postulated that chemical peeling have all been used with varying
Histology: The tumor surrounds a well-formed ter- these two tumors are indeed the same but appear to be results. The recognition of multiple fibrofolliculomas
minal hair shaft. The upper portion of the hair shaft is two distinct tumors due to routine processing and sam- or trichodiscomas necessitates screening for Birt-
slightly dilated. Emanating from the central hair shaft pling at various tissue plane levels. Hogg-Dubé syndrome.

24 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS