An 84-year-old Japanese woman with a family history of pneumothorax presented with multiple pulmonary cysts. She had had an episode of right pneumothorax at the age of 66 years, and had undergone surgery for lung adenocarcinoma at 73 years. After the surgery, her son developed recurrent pneumothorax. We suspected Birt-Hogg-Dubé (BHD) syndrome and recommended genetic analysis for the patient and her son. Genetic analysis performed at another institute confirmed FLCN germline mutations in the mother and son. Histopathological analysis of the lung revealed well-differentiated adenocarcinoma in situ (AIS) that involved BHD-associated cysts. There are very few reports of lung neoplasms in patients with BHD syndrome. Physicians attending BHD patients should be aware of cancer-predisposing conditions, not only in the kidney but also in other organs, including the lung. We report a case of lung AIS, focusing on the histopathological features, and discuss relevant literature.