Embryoma

EMBRYOMA (embryoma), a tumor-like formation belonging to the so-called complex organismoid teratomas (see). As a rule, it is a derivative of all three germ layers, i.e., a tridermoma. In appearance, these formations are either cystic in nature (cystic embryomas) or consist entirely of tissues (often also containing cysts) and have a nodular, lobular appearance. Typical localizations of embryomas are the gonads, the sacral region, the head (orbit, base of the skull), and the anterior mediastinum. In other places (on the neck, in the abdominal cavity organs), embryomas are rare. In the ovaries, embryomas are usually observed in the form of so-called complex dermoid cysts. In the testicles, embryomas have a solid character (cystic embryomas are a rare casuistry here). In the sacral region (posteriorly under the skin or, less commonly, presacrally in the pelvic cellular tissue), as well as in the head region, embryomas sometimes reach enormous sizes by the time of birth and can create significant difficulties during delivery. Microscopically, the presence of very different parts of the embryo in the form of more or less developed tissues and organs can be detected in embryomas. Ectoderm derivatives predominate, namely skin, nervous tissue of the cerebellar or cerebrum structure type, meninges, sympathetic ganglia, eye rudiments, teeth; pieces of cartilaginous and bony tissue, smooth and striated musculature are found. In addition, elements of the respiratory and digestive tracts, formations resembling salivary glands, can often be seen. Thyroid tissue and some other organs have been found. Rudimentary extremities with nails, a scrotum, an anus-like rudiment, etc. are less frequently described. Apparently, lymph nodes and rudiments of such organs as the liver, kidneys, and spleen are completely absent. In embryogenetic terms, embryomas are divided into monogerminal and bigerminal. It is considered that monogerminal embryomas originate from a detached blastoderm of a dividing egg that did not take a direct and complete part in the further formation of the embryo, but began to develop independently and irregularly. Bigerminal embryomas are classified as double monstrosities, where one of the embryos is included in a normally developed fetus. The indicated subdivision into mono- and bigerminal embryomas is practically not always easy, and sometimes entirely impossible, especially since, on the one hand, between mono- and bigerminal embryomas, and on the other hand, between them and the so-called parasitic asymmetrical and symmetrical monstrosities, there exists a whole series of elusive transitions, and often the typical connection sites of twins and the localization of undoubted parasites coincide (see also Inclusio foetalis). Based on the clinical and anatomical picture, embryomas are divided into mature and immature. Mature embryomas consist of tissues identical in maturity to the tissues of the host, grow synchronously with them, and slowly. Immature embryomas are built of tissues of the embryonic type, grow rapidly, can give metastases, and are thus true tumors, blastomas (embryoblastomas, teratoblastomas). They often arise from rudiments that have lain dormant for a long time, or by way of so-called malignant transformation from mature embryomas. Such malignant tumors are especially common in the testicle, where, developing from epithelial inclusions, they have the character of glandular or solid cancer or give rise to a malignant tumor similar in its structure to the so-called chorionepithelioma (see).