Solitary pulmonary caseating granulomas: A 5-year retrospective single-center analysis

Solitary pulmonary caseating granulomas (SPCGs) are a characteristic type of tuberculomas associated with infection with non-tuberculous mycobacteria (NTM) and other microbes; however, their significance remains unclear. The aim of the present study was to describe the clinical characteristics of patients with SPCGs in terms of diagnosis, presence of lung cancer and treatment status. A retrospective analysis of 17 immunocompetent patients with histopathologically confirmed caseating granulomas after undergoing video-assisted thoracoscopic surgery (VATS) was conducted at our center between 2011 and 2015. The patients comprised 10 men and 7 women with a mean age of 59.1±14.4 years. Of the 17 patients, 14 (82.4%) were asymptomatic and the lesions were discovered incidentally. In 2 patients the SPCGs were accompanied by a small satellite nodule (SPCG mean diameter, 16.2±5.1 mm). Mycobacteria, including Mycobacterium tuberculosis (11.8%), Mycobacterium avium (11.8%) Mycobacterium kansasii (23.5%) and other Mycobacterium spp. (5.9%), were isolated from 9 of the patients (52.9%). Concurrent lung cancer was present in 3 patients (17.6%). When microbial agents could not be isolated, the interferon-γ release assay was useful for diagnosis. Positron emission tomography was not found to be useful for differentiating SPCGs from lung cancer, or for differentiating tuberculomas from NTM pulmonary nodules (NTMPNs). NTMPNs in cases of SPCGs were diagnosed more frequently in men. The findings indicate that a course of observation may be sufficient for patients in whom an SPCG from NTM (NTMPN) is identified by VATS. However, the presence of concurrent lung cancer in certain cases indicates that malignancy should not necessarily be excluded, particularly in NTMPNs, and highlights the necessity of aggressive diagnosis by VATS.