Malignancies in congenital cystic adenomatoid malformations (CCAMs) of the lung are rare. We report a 41-year-old male patient with a pulmonary cystic lesion suspicious for CCAM, unrecognized until the patient was 40 years of age, and which subsequently became more consolidated during the interval between initial presentation and surgery.
Microscopic examination of the resected specimen revealed features of type 1 CCAM with a mucinous adenocarcinoma, metastatic to the mediastinal lymph nodes. This case illustrates the importance of prompt surgical resection for all suspected CCAMs, especially those discovered in adulthood.