Psammoma

PSAMMOMA (from Greek psammos - sand), a tumor containing foci of calcification, or so-called psammoma bodies (see Corpora arenacea). Since tumors with such bodies can be of the most diverse nature in terms of histogenesis—such as carcinomas (especially of the ovaries), sarcomas, endotheliomas (especially of the dura mater), fibromas, etc.—it is more correct to speak not of P. as a special tumor, but of psammomatous tumors, for example, of psammomatous carcinoma, psammomatous endothelioma, etc. The site of formation of psammoma bodies is either elements of connective tissue, hyalinized vessel walls, or epithelial cells, their secretions, etc. Usually the bodies appear as concentrically layered calcareous formations, for example, in psammomatous fibroendothelioma of the dura mater (see illustration - separate plate to the article Carcinoma). Less frequently the bodies have the appearance of spines, needles, beams, flasks, cylinders, etc. PSEUDARTHROSIS-see False joint. PSEUDO-(from Greek pseudes - false), a prefix to various terms used to indicate only external similarity between two phenomena. Thus, when speaking of pseudocysts, pseudomyxomas, pseudoparalysis, pseudohallucinations, etc., one means processes and phenomena that only externally resemble a true cyst, myxoma, paralysis, hallucinations, etc. In Russian the prefix P. is translated as 'false,' for example, when speaking of false dropsy, false croup, etc.