TICHOEPITHELIOMA (trichoepithelioma; Greek thrix, trichos of hair - j-an epithelioma) — a benign tumor of appendages of skin.
The term is offered in 1894 to A. Jarisch. In the International histologic classification of tumors of skin (1975) T. divide into two forms: hereditary T. and actually T. Hereditary T. (an adeno-idno-cystous epithelioma) represents multiple defeat of hl. obr. persons, but sometimes also pilar part of the head, neck and front surface of a trunk. Meets at children's age more often. It is usually shown in the form of small multiple, in some cases symmetric, skin nodules.
Actually T. in the form of single small knots can arise on skin of any part of a body, a thicket on a face, it is equally frequent at men and women, is preferential at adults.
Gistogenetichesky communication of T. with follicles of hair does not raise doubts. A source of development of a tumor, according to Lever (W. F. Lever, 1958), primary epithelial rudiment of follicles of hair, according to other data — mature follicles of hair or defects of their development is.
Macroscopically T. has an appearance of the small, with a diameter up to 1 cm, plotnovaty accurately outlined node of light pink or yellowish color, sometimes with small cystous cavities on a section. Microscopic structure of T. very variously. Characteristic gshloidny (in
Fig. Mikropreparat of a tichoepithelioma of skin (a cystous form): 1 — the cystous cavity containing horn masses; 2 — oh-zaliomopodobnye growths; coloring hematoxylin-eosine; x 160,
the direction of follicles of hair) the differentiation can be expressed in various degree: from hardly outlined concentric flat and epithelial structures with keratinization in the center to almost mature follicles of hair with existence of ugly hair cores. Depending on dominance of the relevant structures allocate cystous, clear cell, solid and mixed morfol. options T. This division has no wedge, values, but it is important for morfol. differential diagnosis. Most often the cystous T meets., containing cystous from a peculiar ploskoepitelialny vystilky cavity, filled pale okrashpvayushchimisya with the horn masses (fig). Walls of cystous cavities have uneven thickness, sites of cells of a flat epithelium meet focal keratinization and elements of unripe hair cores. The bazaliomopodobny tyazhisty growths departing from ploskoepitelialny complexes are often observed. Sometimes around tumoral complexes strips are found, similar to the hyaline membranes surrounding follicles of hair are normal. Partial destruction of a tumor due to giant-cell reaction and calcification can take place. Clear cell T. it is characterized by dominance of large polygonal cells with a clear boundary and light cytoplasm, against the background of to-rykh ploskoepitelialny complexes with the central concentric arrangement of cells, keratinization and formation of ugly hair cores are observed. Solid T. meets less often than others. It is formed by solid growths of large and small cells of a flat epithelium with focuses drank-idnoy differentiations — from concentric accumulations of the flattened cells before formation of ugly follicles of hair. In the mixed T. find a combination described morfol. options. The fibrous stroma is usually more expressed in cystous T., in others — it is scanty. Distinctiveness of hereditary T. existence of the anastomosing tubular educations reminding incorrectly created output channels of sweat glands is.
At differential diagnosis with other tumors of skin it is necessary to consider morfol. similarity of T. with bazaliomy (see), clear cell gidradenomy, planocellular cancer (see).
The forecast is favorable, a recurrence is observed seldom.
See also Skin, tumors. Bibliography: And p and t e N to about A. K. Tri -
a hoepiteliom, Arkh. patol., t. 30, No. 10, page 15, 1968; about N e, Epithelial tumors and malformations of skin, M., 1973; In and x e r A. M. t, and l and l - about of l y G. A. and Poroshin K. K. Atlas of diagnostic biopsies of skin, M., 1973; L e-
in e r U. F. Gistopatologiya of skin, the lane with English, M., 1958; J a r i s with h H.
Zur Lehre von den Hautgeschwlilsten, Arch.; Derm. Syph. (Berl.), Bd 28, S. 163, 1894.
V. M. Blinov.