Recurrent Pleural Effusion as the Initial Presentation of T-lineage Lymphoblastic Malignancy in a Child: A Diagnostic...

Pleural effusion in children is most frequently associated with infectious diseases, particularly parapneumonic effusion. Recurrent or unexplained pleural effusion, however, should prompt consideration of less common etiologies, including autoimmune disease, tuberculosis, chylothorax, cardiac and renal disease, and malignancy. We report the case of a 10-year-old boy with recurrent large right-sided pleural effusions requiring repeated drainage of more than 1,500 mL. An extensive diagnostic evaluation for rheumatologic and infectious causes was unrevealing. During the current admission, the patient had anorexia, weight loss, axillary lymphadenopathy, leukocytosis, and mild thrombocytopenia, without reported peripheral blood blasts. Chest computed tomography demonstrated a large right pleural collection, bilateral axillary lymphadenopathy, and prominent thymic tissue without a definite bulky anterior mediastinal mass. Pleural-fluid flow cytometry demonstrated an abnormal immature T-lineage lymphoblast population comprising approximately 99% of analyzed cells. Pleural biopsy showed tissue infiltration by atypical lymphoid cells morphologically resembling non-Hodgkin lymphoma. Subsequent bone marrow examination, performed after three days of methylprednisolone therapy, demonstrated diffuse blast infiltration with an immature T-cell immunophenotype and was diagnostic of T-cell acute lymphoblastic leukemia. Lymph-node biopsy showed lymphoproliferative disease, while lumbar puncture was normal. Pleural-fluid tuberculosis PCR and acid-fast bacilli testing were negative. This case emphasizes that recurrent pleural effusion may be an initial and predominant manifestation of T-cell acute lymphoblastic leukemia, even in the absence of peripheral blood blasts or a typical mediastinal mass. Early pleural-fluid flow cytometry may facilitate diagnosis and prevent diagnostic delay.