Peripheral pulmonary mucous gland adenoma with a cavity mimicking lung cancer

A 71-year-old woman presented to our hospital because of a 10 mm nodule with a cavity in right lower lobe on chest computed tomography. Fluorodeoxyglucose-positron emission tomography showed slight accumulation in the nodule (maximum standard uptake value 2.08). Her serum carcinoembryonic antigen concentration was 5.4 ng/mL. Wedge resection of the tumor was performed for diagnostic and treatment purposes. Findings on intraoperative pathological examination of a frozen section were suspicious for adenocarcinoma. We, therefore, performed a right lower lobectomy and mediastinal lymph node dissection. Postoperative histological examination revealed a mucous gland adenoma. The patient's postoperative course was favorable and she was discharged 7 days after surgery. Four months later, the serum carcinoembryonic antigen concentration had decreased to 3.1 ng/mL. Pulmonary mucous gland adenomas are rarely located peripherally. These benign tumors should be considered, even in the presence of high serum carcinoembryonic antigen concentrations or increased fluorodeoxyglucose uptake on fluorodeoxyglucose-positron emission tomography.