Adenocarcinoma of the Lung Mimicking Miliary Tuberculosis

Miliary shadows on chest imaging have wide differential diagnoses. The most common etiology is infectious, such as miliary tuberculosis (TB) and histoplasmosis, but miliary shadows can be the presentation of sarcoidosis, pneumoconiosis, and secondary metastasis to the lungs from primary cancers of the thyroid, kidney, and trophoblasts as well as sarcomas. Here we present the case of a 35-year-old Indian male who presented with a 2-month history of dry cough and shortness of breath. Chest imaging showed diffuse bilateral miliary nodules. The initial impression was that of miliary pulmonary TB. Subsequent bronchoscopy with a transbronchial biopsy confirmed the diagnosis of pulmonary mucinous adenocarcinoma with brain metastasis, which is a rare and unusual presentation of primary lung cancer. The tumor was positive for ALK5A4 and PD-L1, and the patient was started on tyrosine kinase inhibitor immunotherapy, with a favorable response.