What is the difference between fetus in fetu and fetiform teratoma?

looney_tunes

"Fetus in fetu and fetiform teratoma are rare forms of mature teratoma that include one or more components resembling a malformed fetus. Both forms may contain or appear to contain complete organ systems, even major body parts such as torso or limbs. Fetus in fetu differs from fetiform teratoma in having an apparent spine and bilateral symmetry. Most authorities agree that fetiform teratomas are highly developed mature teratomas; the natural history of fetus in fetu, however, is controversial. ... Regardless of whether fetus in fetu and fetiform teratoma are one entity or two, they are distinct from and not to be confused with ectopic pregnancy." http://en.wikipedia.org/wiki/Teratoma Aug 18 09, 1:45 AM