A case of nontuberculous mycobacterium after resection of colon cancer diagnosed by thoracoscopic biopsy*
We report a case of nontuberculous mycobacterium after resection of colon cancer diagnosed by thoracoscopic biopsy. A 78-year-old man was followed up for 4 years after sigmoidectomy and S4 hepatectomy for sigmoid colon cancer with liver metastasis. Chest CT revealed bilateral multiple pulmonary nodules and mediastinal lymphadenopathy. FDGPET examination showed abnormal accumulation in bilateral hiatus and mediastinal lymph nodes and mild accumulation in the pulmonary nodules. We suspected that the patient had developed sarcoidosis or multiple lung and mediastinal lymph node metastasis. Cytological diagnosis using bronchofiberscopy confirmed the absence of malignancy, but α－hemolytic streptococci were found in blood culture tests. Laboratory examination showed no abnormal findings, including those for tumor marker and ACE. Acid-fast bacillus smears and sputum culture tests were negative. We performed thoracoscopic biopsy of the mediastinal lymph nodes and part of pulmonary S4. Histopathological examination revealed many small nodules on the surface and under the pleural area, leaflet dissepiment, bronchial circumference, and perivascular area of the left lung tissue. Caseation necrosis was seen in the nodal center, while epithelioid histiocytes were present in the circumference. Furthermore, we found hyperplasty of fibrous connective tissue and deposition of coal dust in the circumference of the nodule. We also found a few acid-fast bacilli in the caseation necrosis. The same findings were seen in the mediastinal lymph nodes; however, malignant findings were absent in both tissues. Cheese-like necrotizing granuloma due to acid-fast bacilli infection was seen in pulmonary silicosis nodules. QuantiFERON examination was negative, and we confirmed the presence of pulmonary nontuberculous mycobacterium. Thoracoscopic biopsy is useful for the diagnosis of intrapulmonary multiple nodules and mediastinal lymphadenopathy, and it can be safely performed using an ultrasonically-activated device and bipolar scissors. (Accepted on October 12, 2011)
