Pulmonary mucinous cystadenocarcinoma: an extremely rare tumor presenting as a cystic lesion of the lung.

Pulmonary mucinous cystadenocarcinoma (PMC) is a rare tumor characterized by mucin production. It is similar to tumors of the same name arising in the ovaries and pancreas. Here we describe the 20th case of PMC reported in the English literature. The patient was a 75-year-old woman with a 3-day history of bloody sputum. Chest radiography and computed tomography revealed a cavitary mass 5 cm in diameter in the posterior segment of the right lung. 18F-fluorodeoxyglucose positron emission tomography demonstrated intense uptake in the wall of the lesion. Right lower lobectomy was performed, and the pathology examination revealed this tumor to be a PMC. The preoperative serum CA 19-9 level was 162.3 U/ml (cutoff 37 U/ml) and decreased to 22.8 U/ml after resection. No mutation of epidermal growth factor receptor or K-ras gene was detected. Thoracic surgeons should bear in mind this rare tumor for the differential diagnosis of a pulmonary cystic lesion.