Fetiform Teratoma Presenting as Retroperitoneal Mass in Three- day-old Newborn: A Case Report

Fetiform Teratoma (FT) is an extremely differentiated neoplasm formed due to unsuccessful migration of primordial germ cells during embryological development. Foetus in Fetu (FIF) is a very rare entity in which a non viable foetus gets reabsorbed within a normally developing foetus, thus mimicking reabsorbed twin. Herein, the authors present a case of three-day-old female who presented with retroperitoneal mass and difficulty passing urine. Ultrasonography (USG) revealed a large, well-defined, heterogeneously hypoechoic solid cystic lesion with internal vascularity noted in retroperitoneum. Histopathology confirmed teratoma due to presence of ectodermal, mesodermal and endodermal components. The authors share the difficulties faced in differentiating between both the conditions. It is of utmost importance to identify FIF and FT antenatally and to diagnose the conditions, as early as, possible to provide adequate management on time, as they are potential mimickers of each other.