KERATOACANTHOMA (keratoacanthoma; grech, keras, keratos a horn, horn substance + akantha a thorn + - oma; synonym: molluscum sebaceum, pseudocarcinomatous mollusk, the multiple self-recovering planocellular carcinoma of skin, psevdoepiteliomatozny hyperplasia) — a rare benign tumor of skin, morphologically sometimes reminding the high-differentiated planocellular cancer, capable to be exposed to involution. To. it is for the first time described by A. Dupont in 1930.
Macroscopically To. represents the formation of semi-spherical shape towering over skin, 1 in size — 2 cm, with the crateriform retraction and horn masses in the center (fig. 1); a tumor dense to the touch, on a section of gray-pink color. At microscopic examination it is noted focal acanthosis (see) and sharply expressed hyperkeratosis (a thickening of a corneous layer of an epithelium). Interpapillary shoots of an epithelium get deeply into a derma, often merge with each other, forming fields with uneven contours; the basal layer of an epithelium is badly distinguishable. In the peripheral departments which are intensively growing To. a significant amount of mitoses meets. On certain sites — fields and tyazh of the differentiated cells of an aculeiform layer. These sites can remind growths of the high-differentiated planocellular cancer. In superficial departments of a tumor it is considerably expressed hyperkeratosis (see) owing to what in the center of a tumor the space filled with horn masses — the horn bowl which is morfol, a sign To is formed. (fig. 2). Idiosyncrasy To. also existence of a so-called collar — the site of the epidermis covering the tumor eminating over the surface of skin and which is located on the periphery of a tumor on border with not changed epidermis is. In a derma around a tumor there is an expressed lymphoid and histiocytic infiltration with existence of plasmocytes, eosinophils, and sometimes segmentoyaderny leukocytes, colossal cells of foreign bodys meet. In a phase of regression of a tumor around it granulyatsionny fabric rich with cells develops, edges it is gradually replaced with fibrous. In some cases differential diagnosis between To. and planocellular cancer it is difficult: existence patol, mitoses in cells, their polymorphism and atypias, infiltriruyushchy growth of a tumor testify to a zlokachestvennost of process.
A. K. Apatenko allocated four morfol, forms K.: warty (superficial and deep), papillomatous and mixed. Most of authors considers that To. gistogenetichesk it is connected with epidermis, appendages of skin can be involved in process for the second time.
The tumor is usually single, meets at elderly men more often; multiple To. arise at young people. It is localized To. more often on a face, hands, is more rare — on a trunk and the lower extremities. Development To. begins with formation of the dense, towering over skin node which often have the site of the retraction filled with horn masses in the center. The node quickly grows and in 3 — 4 weeks has 2, 3 cm in the diameter are more rare. During 5 — 12 weeks the tumoral node is flattened, decreases in a size, horn masses disappears and the hem develops. To. sometimes recurs, the malignancy is in rare instances possible. In some cases the new growth remains for many years.
Because the malignancy can come at any stage of development To., regardless of duration of existence, excision of a tumor is recommended; also diathermocoagulation and cryotherapy is applied by liquid nitrogen.
Bibliography: Apatenko A. K. Epithelial tumors and malformations of skin, M., 1973, bibliogr.; Venkey T. and Shugar I. Malignant tumors of skin, the lane with Wenger., Budapest, 1962; Vikhert A. M., and l and l au of of l y G. A. and Poro-sh and K. K N. Atlas of diagnostic biopsies of skin, M., 1973, bibliogr.; The guide to pathoanatomical diagnosis of tumors of the person, under the editorship of N. A. Krayev-sky and A. V. Smolyannikov, page 410, M., 1976; L e v e of W. F. and. S with h and u m b u of g-Lever G. Histopathology of the skin, Philadelphia-— Toronto, 1975.