Fetus-in-fetu (FIF) is a rare entity resulting from abnormal embryogenesis in diamniotic monochorionic twins, being first described by Johann Friedrich Meckel (1800s). This occurs when a vertebrate fetus is enclosed in a normally growing fetus. Clinical manifestations vary. Detection is most often in infancy, the oldest reported age being 47. We report the case of a 4-day-old girl who was referred postnatally following a prenatal fetal scan which had revealed the presence of a multi-loculated retroperitoneal mass lesion with calcifications within. A provisional radiological diagnosis of FIF was made. Elective laparotomy revealed a well encapsulated retroperitoneal mass containing among other structures a skull vault and rudimentary limb buds. Recovery was uneventful. Here we discuss the difference between FIF and teratomas, risks of non-operative therapy and the role of serology in surveillance and detection of malignant change.
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机译：胎儿胎儿（FIF）是一种稀有的实体，是由羊膜单绒毛膜双胎中异常胚胎发生导致的，最早由Johann Friedrich Meckel（1800年代）描述。当脊椎动物胎儿被封闭在正常生长的胎儿中时，就会发生这种情况。临床表现各不相同。检测通常是在婴儿期，最古老的报告年龄是47岁。我们报告了一个4天大的女孩，该例是在产前胎儿扫描后被发现产后转诊的，发现存在多处腹膜后病变并伴有钙化内。初步诊断为FIF。择期剖腹手术显示，腹膜后包膜包好，其中包括颅骨穹and和原始肢芽。恢复情况平稳。在这里，我们讨论了FIF和畸胎瘤的区别，非手术治疗的风险以及血清学在监测和检测恶性变化中的作用。
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