A 67-year-old man was referred to our department after his local doctor detected a 15-mm nodular shadow in the upper lobe of his right lung. The nodule had remained unchanged for 10 months (Fig. 1A and B). The patient's temperature was 36.5  C, his heart rate was 78 beats per minute, and percutaneous arterial oxygen saturation was 98% in room air. Symptoms such as cough, sputum, shortness of breath, and weight loss were not observed. His medical history included hypertension, chronic obstructive pulmonary disease, dyslipidemia, and internal carotid artery stenosis, and he had a history of smoking 20 cigarettes a day for 43 years. His family history was unremarkable. He had no history of pet ownership, overseas travel, or excessive exposure to dust. Laboratory results on admission included a white cell count of 6610/mm3 (reference range 3300-8600/mm3) with white blood cell differentiation ratios of 72.5% neutrophils (reference range 35%-73.0%), 18.3% lymphocytes (reference range 20.0%-52%), 4.2% eosinophils (reference range 0.0%-11.0%), 0.4% basophils (reference range 0.0%-2.0%), 4.6% monocytes (reference range 0.0%-13.0%), and hemoglobin 14.3 g/dL (reference range 13.5-17.0 g/dL), platelet count 192,000/mm3 (reference range 150,000-350,000/mm3), C-reactive protein 0.03 mg/dL (reference range 0.0-0.3 mg/dL), carcinoembryonic antigen 4.26 ng/mL (reference range 0.0-5.00 ng/mL), and cytokeratin-19 fragments 3.3 ng/mL (reference range 0.0-2.8 ng/mL). An interferon-gamma (IFNgamma)-releasing assay (IGRA) (QuantiFERON-TB GoldR) was positive at 0.49 IU/mL. Tests for cryptococcus antigen and HIV antibodies were negative. Chest computed tomography (CT) revealed a 15-mm nodular shadow with slightly irregular margins in the upper lobe of the right lung (Fig. 1). Only normal bacterial flora were detected via sputum culture, and Mycobacterium smear, tuberculosis (Tb)-polymerase chain reaction (PCR), and MAC-PCR were negative, as was acid-fast bacilli culture. Ultrasound-guided bronchoscopy confirmed the locations of the lesions, then transbronchial biopsy, bronchial brushing, and bronchial lavage were performed. Histological investigations did not reveal any indications of malignancy or granuloma, and the cytological results of bronchial washing and brushing were negative for malignancy. Bronchial lavage culture only yielded normal bacterial flora, and a Mycobacterium smear was negative in the culture test as were Tb-PCR, MAC-PCR, and acid-fast bacilli culture tests. Based on these results no definitive diagnosis was reached with regard to the nodular shadow in the upper lobe of the right lung, and therefore the patient was instructed to comply with careful monitoring on an outpatient basis.
The patient was monitored as an outpatient for 18 months, during which time no changes in the size or characteristics of the nodular shadow in the right upper lobe of the lung were observed (Fig. 2A). A small 5-mm node appeared as a new lesion in the left lung apex, however, and it gradually increased to 10 mm over the course of 10 months (Fig. 2B). Enlargement of the right axillary lymph node was also observed. No enhancement effect was detected via contrast CT (Fig. 2C). Accumulation was detected in the left lung apex and right axillary lymph node via positron emission tomography-CT (Fig. 2D), but no accumulation was depicted in the right lung nodule. The patient had no fever, cough, or sputum which could suggest disseminated MAC, and the right axillary lymph node was not painful, therefore blood culture tests for acid-fast bacteria were not performed. QuantiFERON-TB GoldR was slightly elevated at 0.93 IU/mL, and anti-MAC antibodies were positive at 1.51 U/mL (reference range 0.0-0.69 U/mL). Angiotensin-converting enzyme level was 1.9 U/L (reference range 8.3-21.4 U/L) and soluble interleukin-2 receptor level was 478 U/mL (reference range 122-496 U/mL). Combined with the fact that no bilateral hilar lymphadenopathy or skin, ocular, or cardiovascular complications were observed, it was surmised that sarcoidosis was unlikely to be the cause of the lung nodule and enlargement of the right axillary lymph nodes.
The new lesion, which was depicted as a small nodular shadow in the left lung apex, was in contact with the proximal subclavian artery, and performing a surgical lung biopsy to achieve a definitive diagnosis would have been difficult. Hence, a biopsy was obtained from the right axillary lymph node under local anesthesia for diagnostic purposes. Large numbers of epithelioid granulomas and multinucleated giant cells were detected in the biopsy tissue (Fig. 3). M. intracellulare was identified via mycobacterium culture of the biopsy needle aspirate fluid from the right axillary lymph node, therefore lymphadenitis caused by M. intracellulare was diagnosed. Multidrug antimicrobial therapy including clarithromycin was considered, but at the patient's request, his condition was monitored on an outpatient basis instead. Interestingly the nodule in the left upper lobe gradually shrunk over the course of one year, as did the right axillary lymph nodes (Fig. 4A and B). The nodule had almost disappeared after 18 months (Fig. 4C). Anti-MAC antibody was not increased after the left lung apex lesion had disappeared compared to the level recorded when right lymphangitis had appeared (1.45 U/mL vs. 1.51 U/mL; range 0.0-0.69 U/mL). No relapse was observed throughout the 18 months following the biopsy. During the subsequent follow-up period the lesion in the right upper lobe did not exhibit any changes in size or other characteristics (Fig. 1).
A. Chest computed tomography (CT) revealed a 15-mm irregularly shaped nodule in the upper lobe of the right lung. The nodule shadow was unchanged after 10 months of observation.