A Case of a Lung Cyst Associated with Mycobacterium avium Indistinguihsable from Lung Cancer

Abstract

The case involved a 73-year-old woman who presented with a 16 × 10 mm abnormal shadow in the right lung at a medical checkup when she was 71 years old. Detailed examination revealed a right lung mass. Bronchoscopy did not reveal any malignant findings and Mycobacterium avium was isolated from the bronchial lavage fluid. As the patient was asymptomatic, she was advised annual follow-up examinations. At 72 years of age, the patient had cough and sputum, and a sputum culture test revealed the presence of Mycobacterium avium. A chest computed tomography revealed a right lung mass. Therefore, we initiated triple treatment with clarithromycin, ethambutol, and rifampicin. Despite symptomatic remission, the mass persisted, and it increased to 19 × 14 mm in size after another year, when the patient was 73 years of age. Positron emission tomography showed mild FDG uptake in the mass with the SUVmax of 1.8. We performed surgical biopsy, as the mass could have been lung cancer. The pathological diagnosis was a lung cyst with liquid retention. The cyst was considered a cyst associated with the presence of Mycobacterium avium. Therefore, we continued the triple treatment for 1 year. After discontinuing administration, she has remained free of recurrence. Clinicians should consider surgery for making precise diagnosis.