A Newborn with Multiple Fetus in Fetu Supporting the Spectrum Embryological Theory

Fetus in fetu (FIF) is a rare congenital anomaly in which fetal tissue is found within the body of a living newborn or child. This should be distinguished from the highly differentiated teratoma which has a higher risk for malignancy. Distinguishing between the two entities may be a clinical challenge. Diagnosis is often made by ultrasound, computerized tomography (CT) or magnetic resonance imaging (MRI) together with histopathologic findings. Treatment consists of surgical excision. Most cases reported in literature present one FIF, with very few cases of multiple fetuses in fetu. We present a case of a newborn with two cystic abdominal masses compatible with two separate fetuses in fetu according to surgical and pathologic analyses. However, they have different pathological characteristics and therefore this case report may shed some light regarding FIF pathogenesis and a possible new embryological theory.