Intrathoracic extra-mediastinal cystic hygroma in infancy.

An infant with intrathoracic extra-mediastinal cystic hygroma is described. Fluid collection within the fetal chest was noted on routine antenatal ultrasound scan and this was subsequently drained. Postnatally, echocardiogram and thoracic CT scan demonstrated a cystic space between the pericardium and right mediastinal pleura. Thoracotomy performed at six weeks of age showed a multiloculated cystic mass adherent to the right pericardium and to the medial aspect of the diaphragm. Histology revealed the tumour to be a cystic hygroma (lymphangioma). Intrathoracic cystic hygroma occurring outside the mediastinum is extremely rare and has never been diagnosed previously in infancy.