Fetus-in-Fetu: A Case of Ovarian Involvement and Residual Regrowth in a Teenager

Background: Fetus-in-fetu (FIF) is a rare, congenital soft tissue mass typically occurring retroperitoneally in neonates younger than 18 months. We present a 13-year-old girl with an ovarian FIF occurrence and subsequent residual regrowth after resection.Case: A 13-year-old girl presented with abdominal pain and was found to have a 19-cm, complex, right adnexal mass. Preoperative tumor markers were normal and risk assessment favored a benign process. She underwent open ovarian cystectomy with pathology showing FIF. Nine months later, she had a recurrence of her ovarian mass and underwent right oophorectomy, with FIF on pathology.Summary and Conclusion: In patients in whom FIF is discovered within the ovary, consider postoperative surveillance, because of the risk of recurrence or residual disease.