A 62-year-old man visited the emergency department of our hospital in June of 20XX-7 year for a ureteral stone. An abdominal computed tomography (CT) scan showed a mass of 46×34 mm in the lower lobe of the left lung. He was advised to visit our department, but he disregarded this advice. In January of 20XX-3 year, a mass shadow was again detected on chest CT at another hospital, and he was referred to our department. The mass was slightly enlarged compared to the previous CT. It was well circumscribed with a smooth margin, round form, and homogeneous internal density. He did not wish to undergo a biopsy and although he underwent follow-up observation, he later stopped visiting our hospital. In July of 20XX year, cough and left back pain appeared. The same mass shadow was detected on chest CT at another hospital and he was referred to our hospital again. The mass shadow was enlarged, and a low-density area was present in part of the interior. Eleven days later, a cavity had appeared inside the mass. Surgery was performed for confirmation of the diagnosis and for treatment, and this led to the diagnosis of primary pulmonary meningioma. There have been very few reports of this disease, and as far as we could find, no case with cavity formation has previously been reported.