Myxoma

MYXOMA (from Greek myxa—mucus), syn. myxoblastoma, a tumor of mucous tissue, i.e., of tissue containing mucin and corresponding to the Wharton's jelly of the umbilical cord. It is precisely the presence of mucin (see) that determines the classification of a tumor as a true myxoma and makes it possible to distinguish myxomas from the myxoma-like changes of other tumors; the basis of the latter may simply be tissue edema with its transformation into a substance resembling mucus but not containing mucin. Myxomas can be primary, constructed from the very beginning and developing from mucous tissue, and secondary, representing the result of a true mucous transformation of such tumors as fibromas, lipomas, chondromas, and sarcomas. It is even accepted to think that myxomas of such sequential origin, i.e., secondary myxomas, are more frequent tumors than primary myxomas. The question of which myxomas are primary and which are secondary is very difficult to resolve even when fibrous, fatty, and cartilaginous tissues are present in the tumor, since these tissues can also form sequentially in primary myxomas (Borst). Such tumors, containing the aforementioned tissues alongside mucous tissue, are called, depending on the predominance of one or another tissue, either myxoma fibromatodes, lipomatodes, chondromatodes, or fibroma, lipoma, chondroma myxomatodes, or myxofibroma, fibromyxoma, myxochondroma, chondromyxoma, etc. True primary myxomas undoubtedly include mucous tumors developing from embryonic remnants of mucous tissue, e.g., myxomas of the umbilical region, mesentery, bladder wall, and multiple myxomas of nerve trunks. On the other hand, the origin of myxomas arising from subcutaneous tissue, from mucous membranes (e.g., of the nose), from the endocardium, periosteum, bone marrow, interstitial tissue of the mammary gland (e.g., myxoadenomas, which are adenomas with mucification of the stroma), etc., is controversial in terms of their classification as primary myxomas. Many of the formations sometimes called myxomas, such as mucous polyps of the nose or uterus, are not tumors but represent inflammatory hyperplasias of the mucous membrane. Some heart myxomas are nothing more than organized thrombi with subsequent tissue edema. The term myxoma (myxoma chorii) is also incorrectly applied to hydatidiform mole. Myxomas are nodular, often polypoid (e.g., myxomas of mucous and serous membranes) tumors of soft consistency, grayish-pink in color, very succulent, moist on cross-section, often with the discharge of mucous fluid on the cut surface. Microscopically, myxomas consist of a transparent, mucin-containing ground substance in which stellate, triangular, and spindle-shaped cells with thread-like processes, characteristic of mucous tissue, are visible; leukocytes, lymphocytes, and polyblasts are quite often found among these elements in varying quantities. Myxoma tissue is usually very rich in blood vessels; when they are very highly developed, it is called myxoma angiomatodes. The course of a myxoma is benign: typical myxomas do not metastasize and rarely recur after surgery. However, cell-rich myxomas are encountered, in which the cells are polymorphic and contain hyperchromatic nuclei of unequal size; such tumors, which are classified as myxosarcomas, exhibit all the signs of a malignant course characteristic of sarcomas. The treatment of myxomas is surgical.

A. Abrikosov