Perithelioma

PERITHELIOMA, perithelioma (syn.: endothelioma perivasculare, sarcoma angioplasticum, s. peritheliale, angiosarcoma, etc.), a tumor representing a variety of endothelioma, with adventitial, perivascular, multilayered, often radial arrangement of cuboidal, cylindrical, or polygonal cells. It differs from ordinary hemangioendothelioma (intravascular form) in that it preserves the endothelium of blood vessels, from the walls of which the proliferation grows. - The name perithelioma cannot generally claim definiteness, since firstly, the relationship between the so-called perithelial cells and adventitial cells of vessels has not been clarified, secondly, it has not yet been histologically and genetically established whether the 'perithelium' is identical to or different from the endothelial lining of lymphatic spaces in the adventitia of blood vessels, thirdly, perithelium is known in the brain, meninges, and testicle, while peritheliomas have been described in other organs. The connective tissue nature of perithelium, which normally consists of polymorphic, round, spindle-shaped, and flat cells arranged in a single layer, is confirmed by its ability to form fibrils that appear in some cases between groups of perithelioma cells and give the tumor an alveolar structure. - Many identify perithelioma with angiosarcoma, but in the latter there is no genetic relationship between the vessels and tumor cells, as in perithelioma, which can therefore be considered one of the types of angioplastic sarcoma or sarcomatous angioma (sarcoma peritheliale). However, it is very rarely possible to establish the angioplastic nature of perithelioma growth. Sometimes it is difficult to distinguish it from certain forms of papillary carcinoma, especially at the beginning of its formation, and from sarcoma, particularly with further tumor growth when adjacent layers of perivascular cells merge with each other. Clinically, peritheliomas are relatively benign, although they can give locally destructive growth and persistently recur; they are little inclined to generalization; however, malignant-medullary, infiltrating, metastasizing peritheliomas also occur. Peritheliomas are rich in blood, have a spongy appearance and soft consistency, are prone to mucoid and hyaline degeneration, with degenerated vessels often taking the form of solid hyaline cylinders (cylindromas). Peritheliomas occur predominantly in the meninges, in plexus chorioideus, in the brain; less frequently - in the skin, muscles, bones, serous membranes, and in many organs (breast gland, salivary glands, lymph glands_g stomach, liver, kidneys, adrenal glands, ovaries, uterus, vagina, etc.), either as individual nodules or in multiple and diffuse forms. Peritheliomas of the dura mater and pia mater of the brain and spinal cord occur in the form of small single or multiple nodules. In some cases here, peritheliomas take on a papillary character (papilloma piae matris perivasculare). In bones, peritheliomas as primary tumors are rare, belonging to the type of central (myelogenous) sarcomas; sometimes the cells of bone perithelioma are cylindrical in shape, almost epithelial in appearance, arranged exactly radially in relation to capillaries (the so-called primary bone carcinomas of some authors). In the skin, peritheliomas can reach large sizes (up to the size of a fist), consisting of wide capillaries surrounded by radially arranged cells of various shapes. Peritheliomas of the kidneys often raise doubts about the classification of the tumors as hypernephromas or carcinomas. The same can be said about peritheliomas of the ovaries (these are often ovarian carcinomas). Previously, tumors of the carotid gland and coccygeal gland were classified as peritheliomas, but the structure of these tumors corresponds to the normal gland (see Carotid gland).

i. poznakin.