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Acanthoma of the hair follicle sheath: causes, symptoms, diagnosis, treatment
Last reviewed: 07.07.2025
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The tumor was named by A. Mehregan and M. Brownstein in 1978. Clinically, the tumor looks like a nodule measuring 0.5-1 cm with a depression in the center. The age of patients is 30-70 years, the frequency in men and women is approximately the same, localization is the skin of the upper lip, forehead, neck, and auricles. In this case, the most common diagnosis is comedone, enlarged burrow, cyst, basalioma.
Pathomorphology of acanthoma of the hair follicle sheath. In the center of the neoplasm there is a crater-like expanded funnel of the follicle with a normal lining of epithelial cells, compact orthokeratosis and hypergranulosis. From the epithelial lining of the funnel, clearly delimited complexes of keratinocytes extend radially into the surrounding dermis up to the subcutaneous adipose tissue, surrounded on the periphery by stripes of fibrous tissue, giving the complexes a lobular appearance. On the skin of the face, the lobules can penetrate to the level of skeletal muscles. Keratinocytes that form the lobules may resemble cells of the funnel or isthmus of the hair follicle. Along the periphery of the lobule, the cells are oriented radially. In the central part of each lobule there are usually cyst-like structures delimited by a narrow rim of cells containing keratohyalin granules. Often there are single or small groups of sebaceous cells, scattered necrotic keratinocytes, similar to those in the outer shell of the follicle in the catagen stage. Occasionally, rudimentary hair follicles and papillae can be found on the periphery of the complexes.
Differential diagnostics are performed with solitary keratoacanthoma, which can also have a wide funnel filled with horny masses. However, it lacks signs of follicular differentiation, and cellular elements can have nuclei with signs of atypia, mitotic figures. At the base of the cellular complexes there is a dense inflammatory infiltrate, trichofolliculoma is distinguished by the presence of many well-formed vellus follicles.
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