[Pulmonary infection with Mycobacterium kansasii presenting as solitary nodule shadow in the left anterior basal segment].

A 71-year-old man was admitted to our hospital for evaluation of a solitary pulmonary nodule in the left lower lung field. He had been treated for Parkinson's disease for two years, and had no respiratory symptoms on admission. No abnormal findings were detected in laboratory tests on admission, and Mantoux's skin test was negative. A postero-anterior chest roentgenogram, a conventional tomogram, and a computed tomogram showed that the nodule was located in the left anterior basal segment (S8). The nodule was not calcified, the contour was clear but irregular, and pleural indentation could be seen, so the nodule was strongly suspected to be a primary malignant lung tumor. Because two attempts at transbronchial lung biopsy and bronchial brushing and washing were of no diagnostic value, a thoracotomy was done. The lesion was found in the subpleural region of the left S8 with pleural indentation, and it was partially resected. The nodule was elastic, soft, and filled with suppurative fluid. Histopathologic examination of the nodule revealed epithelioid cell granuloma. A smear test of the fluid was negative but a culture was positive for mycobacteria; which were identified as Mycobacterium kansasii. Rifampicin and isoniazid were administrated to the patient for 1 year. Two years after the operation, the patient was asymptomatic.