Pulmonary tuberculosis presenting as an enlarging left lower lobe mass-like lesion mimicking malignancy

Pulmonary tuberculosis (TB) classically involves upper lobes in reactivation disease, but it can rarely present as a mass-like consolidation that closely mimics lung malignancy. A 59-year-old man born in the Philippines and living in Nevada with poorly controlled type 2 diabetes mellitus (HbA1c 9.8%) and COPD was found to have an incidental 4.0 × 3.0 cm left lower lobe (LLL) mass-like lesion with mildly enlarged lymph nodes. An interferon-gamma release assay (IGRA; QuantiFERON-TB Gold Plus) was negative. Initial bronchoscopy with bronchial washings was negative for acid-fast bacilli (AFB) culture, Gram stain, and fungal studies. Seven months later, he developed progressive productive cough, night sweats, dyspnea, fatigue, and weight loss. Repeat CT demonstrated interval enlargement of the LLL lesion to 7.8 × 6.2 cm with new scattered opacities. Repeat bronchoscopy with biopsy demonstrated granulomatous inflammation with AFB, and Mycobacterium tuberculosis nucleic acid amplification testing (NAAT) was positive; AFB smear was positive and culture confirmed fully susceptible TB. The patient was managed with airborne isolation precautions and started on rifampin, isoniazid, pyrazinamide, and ethambutol (RIPE), with rapid clinical improvement. Follow-up CT was deferred at the patient's request due to concerns about cumulative radiation exposure, given his significant symptomatic recovery. This case reinforces maintaining TB on the differential diagnosis of enlarging lung masses-particularly in patients with epidemiologic risk factors and immunometabolic comorbidity-and highlights the value of repeat sampling, tissue diagnosis, and NAAT in atypical presentations.