Congenital cystic adenomatoid malformation in adults, presenting as a single cyst

Congenital cystic adenomatoid malformations are lung anomalies usually detected prenatally or in newborns and infants. Type 1 congenital cystic adenomatoid malformations appears as a multicystic lesion, with cysts up to 2 cm in diameter, or as a single large cyst. In the latter case, when detected in adults, the preoperative diagnosis is challenging because congenital cystic adenomatoid malformations can be confused with other more common lesions. We describe two cases of uniloculated type 1 congenital cystic adenomatoid malformation in adults. In both cases, the preoperative clinical diagnosis was missed and the patients were surgically treated with lung-sparing cyst resections.