Bronchoalveolar Lavage Fluid Caseating Granulomas in A Case of Pulmonary Tuberculosis

Pulmonary tuberculosis (TB) is a common infectious disease that is considered one of the leading causes of morbidity and mortality worldwide. Special diagnostic studies for TB can be used including smear microscopy and cultures for acid fast bacilli (AFB) and Mycobacterium tuberculosis (MTB) nucleic acid amplification test (NAAT). The specimen is usually taken from the sputum but might also include pleural and bronchoalveolar lavage (BAL) fluids. In addition, BAL cytology and lung biopsy are commonly done if bronchoscopy is performed. Here, we present a case of suspected pulmonary TB in a patient who was complaining of cough and hemoptysis for several months. Chest x-ray showed right upper lung opacity with cystic changes that was confirmed by CT chest. Work up done for this case included three samples of sputum and one BAL fluid specimen for AFB smear microscopy, culture and NAAT in addition to transbronchial lung biopsies and they were all negative. However, Cytologic examination of BAL fluid using Papanicolaou stain surprisingly showed evidence of intact caseating granulomas characteristic for tuberculous infection. Ultimately, the patient was started on the standard anti-TB regimen for 6 months with significant clinical improvement confirming TB diagnosis. To the best of our knowledge, this unusual cytologic finding in culture-negative BAL fluid coupled with unremarkable lung biopsy and persistently negative sputum samples for TB was never reported in the English literature.