Adenocarcinoma in situ in type I congenital pulmonary airway malformation.

Congenital pulmonary airway malformation, previously known as congenital cystic adenomatoid malformation, is a rare developmental anomaly of the lower respiratory tract. Widespread use of ultrasonography in the prenatal period has increased the rate of early diagnosis of congenital pulmonary airway malformations, thus adult presentation of this condition is extremely unusual. Adenocarcinoma in situ is seen very rarely in adolescent and adult patients with long-standing congenital pulmonary airway malformations. We describe a 28-year-old man with type I congenital pulmonary airway malformation with pulmonary Kirsten rat sarcoma viral oncogene homolog mutation positive mucinous adenocarcinoma in situ.