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

OBJECTIVES: 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. METHOD: 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. RESULTS: 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. CONCLUSION: 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.