OBJECTIVE: To present a case of tuberculosis infection that manifest as mediastinal mass.
CASE: A 5 months old baby was referred to our institution for further evaluation and management of mediastinal mass. The patient suffered from recurrent productive cough and shortness of breath since three months prior to admission. Chest CT scan one month before admission revealed bulky mediastinal mass suggestive of Lymphoma. The patient received methylprednisolone from our pediatric hematology-oncology division for one week but no improvement was observed. Workup for Tuberculosis infection with IGRA came out negative while GeneExpert yield positive result. A repeated CT Scan showed a heterogenous mediastinal mass 7,1 x 6,5 x 6,5 cm in dimension that attached to the right visceral pleura and pericardium. A transthoracal core biopsy was done and the result was consistent with chronic inflammation with granulomatous appearance. The patient was given oral antituberculosis drug and clinical improvements were seen. The patient was discharged after finishing the intensive phase.   
CONCLUSION: Tuberculosis should be considered as a possible diagnosis in an infant presenting with mediastinal mass. Core biopsy is the modality of choice in establishing diagnosis in patients with mediastinal mass.