T-cell lymphoblastic lymphoma with elevated adenosine deaminase concentrations mimicking tuberculous pleural effusion: a case report

T-cell lymphoblastic lymphoma (T-LBL) is a rare non-Hodgkin lymphoma that requires rapid and accurate diagnosis and treatment. A quickly progressing mediastinal mass, body cavity effusions, and cervical lymphadenopathy are major manifestations of T-LBL. We report a 47-year-old male patient with a severe pleural effusion (PE), a small pericardial effusion, and a bulky mediastinal mass, but with a high level of adenosine deaminase (ADA) in the pleural fluid and a positive SPOT-Tuberculosis test (T-SPOT. TB test) and tuberculin skin test (TST). The possibility of tuberculous pleural effusion (TPE) was initially considered. However, the cell block (CB) method in combination with immunohistochemistry indicated that the pleural fluid was positive for CD1 alpha, CD3, and CD99; weakly positive for terminal deoxynucleotidyl transferase (TdT); and negative for CD20. Ultrasound-guided biopsy of the mediastinal mass followed by immunohistochemistry was further performed, confirming the diagnosis of T-LBL. Cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) chemotherapy was initiated and led to progressive remission. This case highlights the notion that elevated ADA levels in PE should be cautiously considered as TPE in the absence of microbiological/histopathological confirmation, and that CB in combination with immunohistochemistry can enhance the diagnostic yield in cases of malignant PE.