Fetal Inclusion

INCLUSIO FETALIS (Latin: fetal inclusion), a developmental anomaly consisting of the fact that in the body cavities of an externally normally developed fetus ('autosit'), separate parts of another fetus ('parasite') are found; this includes, for example, certain teratomas of the mediastinum, ovaries, testicles (with parts of the gastrointestinal tract, facial bones, pelvic organs, etc.). It is considered most probable that the basis of such anomalies lies in a disturbance of the cleavage process of the egg, as a result of which individual blastomeres of the latter, falling out of their usual connection with neighboring cells, implant in a new place, subsequently developing into the corresponding teratoid formation (I. f.). The development of rudiments of the new fetus occurs either simultaneously with the developing normal fetus or later, in the already developed fetus-autosit. Some authors suggest the possibility of development of I. f. at a later period (so-called teratomas of adults, Askanazy). In addition to the usual symptoms of a tumor (for example, compression of adjacent parts), I. fetalis can serve as the initial material for the development of true malignant neoplasms: inflammatory processes, etc., may arise in them.