Heterogeneous echotexture in the EBUS feature (53% versus 13% p<0.001) and coagulation necrosis signs (26% versus 3% p<0.001) in specimens obtained by EBUS-TBNA are suggestive of TB rather than sarcoidosis.
Sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy for TB were found to be 56%, 100%, 100%, 81% and 85%, respectively. TB-PCR using endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) samples is a novel technique in the differential diagnosis of intrathoracic granulomatous lymphadenopathy. The granulomas of TB are typically necrotising, randomly located or bronchiolocentric and may also involve blood vessels. Detection of Mycobacterium tuberculosis in sputum, bronchoscopy specimens, gastric secretions or pleural fluid is necessary for a confident diagnosis. Typical radiological findings for TB include focal infiltration of the upper lobe(s), cavitation, tissue destruction, fibrosis with traction bronchiectasis, enlargement of hilar/mediastinal lymph nodes, small nodular lesions and pleural effusions. In general, prolonged cough, lymphadenopathy, fevers, night sweats and weight loss are suggestive of TB, but are nonspecific. Initiation of a diagnostic evaluation for TB is usually based on a suspicion of TB from epidemiological, clinical and radiographic findings. If microbiological culture is not available, PCR is the only method for differentiating the organisms. Mycobacteria can grow in culture even when specific staining yields negative results. Currently, the only definitive methods for differentiating mycobacteria are microbiological culture and PCR. However, tuberculous mycobacteria and NTM are morphologically similar and often undistinguishable. When mycobacteria are identified, the next step is to differentiate tuberculous mycobacteria from nontuberculous mycobacteria (NTM). Auramine–rhodamine fluorescence shows greater sensitivity than Ziehl–Neelsen staining, although specificity is lower (auramine–rhodamine: sensitivity 80% and specificity 84% Ziehl–Neelsen: sensitivity 60% and specificity 98%). The PAS stain can detect the cell walls of living fungi, whereas the GMS stain detects the cell walls of both living and dead fungal organisms. The periodic acid–Schiff (PAS) stain is also a useful histochemical stain for fungi. The histochemical stains commonly used for the pathological evaluation of infective organisms are the Grocott methenamine silver (GMS) stain for fungi and the Ziehl–Neelsen stain for mycobacteria. Clinicians should note that tuberculosis (TB) may also show nonnecrotising granulomas, depending on the immune status of the patient.
Although infectious lung diseases can show both necrotising and nonnecrotising granulomas, necrotising granulomas are more likely to be associated with infectious lung diseases.
The most frequently found organisms in pulmonary granulomas are mycobacteria and fungi. As granuloma alone is a nonspecific histopathological finding, the multidisciplinary approach is important for a confident diagnosis.Īs infection is a common cause of pulmonary granulomas, it is always important to exclude infectious lung diseases. Bronchoalveolar lavage, endobronchial ultrasound-guided transbronchial needle aspiration, transbronchial cryobiopsy, positron emission tomography and genetic evaluation are potential candidates to improve the diagnostic accuracy for granulomatous lung diseases. Differential diagnosis is challenging, and includes both infectious (mycobacteria and fungi) and noninfectious lung diseases (sarcoidosis, necrotising sarcoid granulomatosis, hypersensitivity pneumonitis, hot tub lung, berylliosis, granulomatosis with polyangiitis, eosinophilic granulomatosis with polyangiitis, rheumatoid nodules, talc granulomatosis, Langerhans cell histiocytosis and bronchocentric granulomatosis). Precise clinical evaluation, laboratory testing, pulmonary function testing, radiological imaging including high-resolution computed tomography and often histopathological assessment contribute to make a confident diagnosis of granulomatous lung diseases. Granulomatous lung diseases are a heterogeneous group of disorders that have a wide spectrum of pathologies with variable clinical manifestations and outcomes.