Teratoma

TERATOMA (from Greek teras - wonder), a complex tumor from the group of mixed tumors, consisting of a systemic composition of many tissues (connective, epithelial, muscular, nervous, etc.) and being a product of violations in embryonic development. The formation of T. is associated with displacements, aberrations, or shutdowns of germ layers, the differentiated derivatives of which have a systematoid character, causing the inclusion in the tumor composition of areas that, microscopically and often macroscopically, correspond to the structure of various organs and tissues: skin with its appendages, muscles, teeth, nervous tissue, sections of the digestive tube, bone, cartilage, etc.; liver, kidneys, pancreas, heart are rarely encountered. T. may originate from two germ layers - bidermoma, or from all three - tridermoma. The earlier the displacement or shutdown of the germ leaflets occurred, the more complex the composition of the tumor. Therefore, among T. there are those in which the formation of separate organ-like parts (organoid T.) is realized, and those that reflect the composition of a whole body area or a whole embryo (organismoid T.). The most complex in composition and structure are T., originating from the earliest stages of cleavage of the fertilized egg (blastomere) or from the primary germ cells. Such T. are called bigerminal (heterochthonous), in contrast to the more simply constructed - monogerminal (autochthonous) teratomas: for the former, the 'teratogenetic terminal point' (see Teratology) is before gastrulation, for the latter - after it. The explanation for this lies in the totipotency of the teratogenic material of early embryonic phases, which in this respect approaches the totipotent egg cell, and in the more limited potency of the embryonic detachments of later phases; in this case, the composition of T. is determined and limited by the formative potential of one of the already formed germ layers, which provides material for the teratoma. Thus, for T., as for all embryonic mixed tumors, a characteristic feature is the genetic connection of all tissues included in its composition, due to the unity of their developmental source. Forms of T. In a number of cases, the systematoidly complexed tissues of T. are immature, having embryonic or even early embryonic structure and forming organ rudiments also of embryonic structure. Such T. represent true tumors with all signs of malignancy, sometimes being the source of special malignant growths either in the form of cancer- or sarcoma-like clusters of embryonic cells, or in the form of malignant neuroepithelial formations, or in the form of chorioepithelioma, etc. Such T. are called blastomatous T. or teratoblastomas or teratoids, in contrast to simple T. (t. simplex, t. adultum). The diversity of combinations of mature and immature areas, the combination of elements of deformity with elements of a true tumor do not always allow distinguishing T. from other mixed tumors; the characteristic feature in such cases is the main sign of T. - the formation of organs or systems of organs. Teratoblastomas mostly have the appearance of small-cystic formations of greater or lesser size, are sometimes detected immediately after the birth of the child or at various times after birth. Their localization: ovary, testicle, choroid plexus of the ventricles, pituitary gland, pineal gland, eye orbit, neck area, oral cavity, jaws, thyroid gland, mediastinum, sacral area, abdominal cavity and other areas of the body. Hormonal products of endocrine glands included in the composition of teratoblastomas can exert a corresponding influence on the body of the tumor carrier. The development of such a tumor in the pineal gland is, for example, the cause of the onset of early sexual maturity. In contrast to teratoblastomas, where the tissues included in the tumor are less mature than the tissues of the tumor carrier, another series of T. consists of fully mature tissues, forming organs of macro- or microscopic size (t. adultum, s. coaetaneum). In some forms of such T., the skin with its appendages predominates in composition: sebaceous and sweat glands, hairs. They have the appearance of cysts, so-called 'dermoid cysts', lined with skin and filled with skin sebum and hairs. On the inner wall of the cyst there is a solid formation of greater or lesser size, in which, upon microscopic and sometimes macroscopic examination, various components of the embryo (skull bones, brain, oral invagination with tongue and teeth, respiratory tube, etc.) can be found. Sometimes rudiments of organs of the anterior or posterior half of the body are found. Such a body, called 'Wilms' villus', sometimes consists of only one tooth, indicating the origin of the dermoid cyst from several germ layers; the other derivatives either did not develop (abortive forms) or underwent reverse development. Such complex dermoid cysts are not true tumors, but only tumor-like developmental defects, standing on the border with the formation of twins. They are most often found in the ovary, sometimes being multiple there, and in the mediastinum, more rarely in the fallopian tubes, large intestine, urinary bladder, very rarely in the testicle.