It is important to distinguish tumour recurrence from other conditions that could show high accumulation on 18F‐fluorodeoxyglucose‐positron emission tomography (FDG‐PET). We describe the case of a 78‐year‐old woman who underwent partial resection of the left lower lung lobe for carcinoid treatment 20 years previously. Five years earlier, chest radiography revealed an abnormal shadow, and chest computed tomography (CT) showed partial atelectasis in the left S8. Periodical CT showed that the atelectasis had developed into a mass. The patient was referred to our hospital. A mass of 45 mm diameter was detected on CT and it had a maximum standardized uptake value of 8.91 on FDG‐PET. We suspected recurrence and performed surgery. Pathological examination revealed epithelioid cell granuloma (maximum diameter, 25 mm) with necrosis. Tissue culture showed no evidence of Mycobacterium tuberculosis . However, serum anti‐MAC antibody level was elevated, suggesting epithelioid cell granuloma caused by non‐tuberculous Mycobacterium infection.