Intrathoracic fetus in fetu cases found in paediatric population: a systematic review

The fetu in fetu (FIF) expression refers to an extremely rare congenital phenomenon characterized by a second fetus growing into the body of the healthy twin. This study aimed to review the few cases located in the thoracic cavity.

Using the central medical databases PubMed/Medline, Web of Science, Scopus, ScienceDirect, and Google Scholar, as well as the references of the articles, we collected only 9 cases of FIF in pediatric patients' thorax. The inclusion criteria were full-text literature and participants aged 19 years or younger. Intra-abdominal or extra-thoracic cases and the presence of malignant components were our exclusion criteria.

Only one case was diagnosed in adolescence. The remaining participants were younger than 10 months at the time of the intervention. There were 4 male, 3 female, and 2 non-declared sex cases. The entire mass was found in the mediastinum, but one was located intrapulmonary. All cases had undergone the thoracotomy. The minimum survival reported in the literature was 5 months. Adipose tissue was the most frequently reported tissue among the resected masses, with 8 cases, followed by the vertebral column and bony tissues, with 6 and 5 cases, respectively.

An infant suffering from respiratory distress or even recurrent infections, particularly with a mass revealed in its chest radiography, should raise a suspicion of FIF. This doubt will be strengthened if an axial skeleton or bony densities are found.