Atypical mediastinal mass in the fetus: a review of the literature

Objectives: Congenital thoracic masses (CTMs) are suspected in presence of solid or cystic thoracic lesions at ultrasound. The common typical fetal CTMs encompass: hyperechogenic lung lesions such as congenital pulmonary airway malformation (CPAM), broncopulmonary sequestration (PS) and congenital high airway obstruction syndrome (CHAOS); less common solid thoracic masses are mediastinal/pericardial tumors as rhabdomyoma and teratoma. The aim of our study is to gather the available evidence on cases of atypical CTMs of difficult classification, for which the diagnosis remains often uncertain. Methods: A review of the literature on the prenatal diagnosis of CTMs was performed, focusing on ultrasound features, postnatal manifestation, treatment and neonatal outcome. Inclusion criterion was prenatal diagnosis of CTM cases with difficult classification in six typical categories. A summary of results was carried out. Results: The literature review included six studies in the analysis. Two cases experienced intrauterine fetal death, one with hydrops in rhabdomyoma and another one for a rapid growth of the mass, with autopsies precising the diagnoses. In two other instances, surgery after birth provided also different histologic diagnoses. All surviving children were asymptomatic at follow-up. One case with rhabdomyoma and another one with atypical pericardial teratoma showed spontaneous regression. Moreover we are presenting our unpublished case of an atypical mass diagnosed as rhabdomyoma or broncopulmonary sequestration. Conclusions: Some masses may present atypical presentation of a known disease or we may face rare diagnosis for which there is lack of information in the literature. The definitive diagnosis still relies on histologic analysis.