Fetus in fetu: a case report

A 2 month old girl with an abdominal mass since birth, was referred to the Cancer Institute with a suspected diagnosis of a Wilms' tumor. Conventional radiograph of the abdomen revealed a mass containing numerous calcifications. CT scan showed a heterogeneous retroperitoneal mass containing well-defined calcified structures. The decision was made to recommend surgical exploration and the mass was successfully excised. Physical examination of the mass with review of literature confirmed the diagnosis of fetus in fetu.Although it is a rare condition imaging may play an important role in the correct prospective diagnosis of fetus in fetu. Surgical excision is the recommended treatment.To our knowledge fetus in fetu was originally described by Meckel in the late 18th century [1]. Fetus in fetu, a term quoted by Willis [2], was first described as a rare condition in which a malformed parasitic twin was found inside the body of its partner usually in the abdominal cavity. It represents an aberration of monozygotic diamniotic twinning in which unequal division of the totipotent inner cell mass of the developing blastocyst leads to the inclusion of a smaller cell mass within a maturing sister embryo.This pathology is rare and the incidence is 1 per 500 000 births [3], with fewer than 100 reported cases worldwide [4]. The majority of cases occur in infancy, with the oldest reported case occurring in a 47-year-old man [1].Tharkral et al [5] reported equal male and female prevalence. In 70% of cases, the chief presenting complaint was an abdominal mass [6]. The mass was predominantly retroperitoneal in 80% of cases [2], while reported uncommon sites include the oral cavity [1], sacrococcygeal region [7], and scrotum [4].A two month old girl was hospitalized because of an abdominal mass present since birth. On physical examination, a smooth, firm, nontender, right flank mass was present.Conventional abdominal radiography showed a large right abdominal mass, which was predominan