Fetus in fetu

A fetus in fetu can be considered alive, but only in the sense that its component tissues have not yet died or been eliminated. Thus, the life of a fetus in fetu is akin to that of a tumor in that its cells remain viable by way of normal metabolic activity. However, without the gestational conditions in utero with the amnion and placenta, a fetus in fetu can develop into, at best, an especially well differentiated teratoma; or, at worst, a high-grade metastatic teratocarcinoma. In terms of physical maturation, its organs have a working blood supply from the host, but all cases of fetus in fetu present critical defects, such as no functional brain, heart, lungs, gastrointestinal tract, or urinary tract. Accordingly, while a fetus in fetu can share select morphological features with a normal fetus, it has no prospect of any life outside of the host twin. Moreover, it poses clear threats to the life of the host twin on whom its own life depends. == Hypotheses of development ==

There are two main hypotheses about the development of fetus in fetu. Teratoma hypothesis Fetus in fetu may be a very highly differentiated form of dermoid cyst, itself a highly differentiated form of mature teratoma. Parasitic twin hypothesis Fetus in fetu may be a parasitic twin fetus growing within its host twin. Very early in a monozygotic twin pregnancy, in which both fetuses share a common placenta, one fetus wraps around and envelops the other. The enveloped twin becomes a parasite, in that its survival depends on the survival of the host twin, by drawing on the host twin's blood supply. The parasitic twin is anencephalic (without a brain) and lacks some internal organs, and as such is unable to survive on its own. ==Case studies==

Sanju Bhagat Sanju Bhagat (b. 1963) is an Indian man who gained public attention after doctors discovered that his abdominal swelling, which was initially suspected to be a tumor, as fetus in fetu. In 1999, Sanju Bhagat sought medical treatment in Mumbai due to severe abdominal enlargement accompanied by breathing difficulties. However, during the surgical procedure, doctors identified the presence of a mass containing differentiated anatomical structures such as limbs, hair, and bone elements. In this case, the enclosed twin had remained undetected for several decades and had established a vascular connection with the host. Following surgical removal of the mass, Bhagat's symptoms subsided, and he recovered without complications. == References ==