Highly differentiated sacrococcygeal teratoma.

Sacrococcygeal teratoma is a well known entity and both its diagnosis and management have been thoroughfully described. Special mention deserves the highly differentiated teratoma as it presents complex organized tissular structures making it slightly different from the classic teratoma although it does not reach the defining characteristics of fetus-in-fetu.A female newborn without prenatal diagnosis presented sacro-coccygeal mass. X-ray image showed bone structures resembling tibia and fibula within the mass. She undertook surgery two days after delivery. Macroscopically, the mass showed besides the bones described on X ray image, cartilaginous structures, some loops of bowel and tissue resembling a finger. There were also some cystic areas. Highly differentiated teratoma also called fetiform teratoma seems to be a defined entity apart from the classical sacrococcygeal teratoma and the fetus-in-fetus. However differences regarding physiopathological and clinical aspects have not been yet completely described.