Primary mediastinal T-ALL presenting with superior vena cava syndrome.

Superior vena cava syndrome (SVCS) is a rare but serious condition typically associated with malignancy. While lung cancer and lymphoma are common causes, less frequent aetiologies can present a diagnostic challenge. We report a case of a young adult female who presented with classical symptoms of SVCS, including facial oedema, neck vein distention and dyspnoea. Diagnostic workup revealed a large mediastinal mass, which was subsequently confirmed as T cell acute lymphoblastic leukaemia (T-ALL) on biopsy. This case highlights the importance of considering T-ALL in the differential diagnosis of SVCS, particularly in younger individuals without traditional risk factors. Early recognition and prompt initiation of appropriate therapy, including chemotherapy and potentially radiation therapy, are crucial for optimal patient outcomes. This case underscores the need for a high index of suspicion for rare malignancies, even in the context of common presentations.