Pulmonary Mycobacterium avium Complex Disease Requiring Differentiation from Recurrence of Lung Cancer during the Follow-Up Period for Lung Cancer

Abstract

Case 1 was a 49-year-old woman who visited with a dry cough. She had an underlying disease of lung adenocarcinoma and received cancer immunotherapy because of an ALK-positive response and several cancer chemotherapies. The clinical effect was a complete response. Chest CT was performed because of continuous dry cough, and a new tumor shadow was recognized in the lingula portion of the left upper lobe. We performed CT-guided lung biopsy and could aspirate pus-fluid. The culture test for acid-fast bacilli was positive and the causative microorganism was identified as Mycobacterium avium by the DDH method. The final diagnosis was pulmonary abscess due to M. avium. Treatment using combined chemotherapy including CAM was performed and a good clinical response was obtained. Case 2 was a 67-year-old man who had a past history of surgical resection of lung adenocarcinoma eight and two years ago and received several cancer chemotherapies and radiation therapy. Because a new nodular shadow appeared in the right middle lobe one year ago and showed strong positivity on PET/CT, surgical resection was performed with the suspected recurrence of lung cancer. Subsequently, the histological diagnosis was epithelioid granuloma and a culture test of acid-fast bacilli was positive, with the identification of Mycobacterium intracellulare by the DDH method. Combined chemotherapy was not performed because the lesion was completely resected. Afterwards, a new nodular shadow appeared in the left lower lobe again and bronchoscopy was performed. Because M. intracellulare was isolated from the local specimen, we diagnosed the patient with recurrence of pulmonary MAC disease and combined chemotherapy including CAM was performed for one year. Finally, the nodular lesion disappeared. It is difficult to differentiate pulmonary MAC disease from lung cancer. Therefore, careful follow-up of patients with lung cancer while keeping in mind the possible complication of pulmonary MAC disease is necessary.