T-cell lymphoblastic lymphoma is an uncommon lymphoid neoplasm in adults, although more frequent in children and teenagers, that often affects the mediastinum and bone marrow, requiring intensive chemotherapy protocols. Its prognosis is poor if a cure is not achieved with first-line treatments. We present a case report of a 19-year-old man diagnosed with this type of lymphoma due to significant respiratory distress and a mediastinal mass. He received treatment according to the hyper-CVAD regimen, with a complete metabolic response. However, seven months later a new mediastinal growth was observed, leading to salvage treatment with a combination of nelarabine and daratumumab. We observed not only refractoriness, but also leukemization, which prompted consideration of hematopoietic stem cell transplantation. Based on this case, we conducted a review of pharmacological treatment options for refractory or relapsed lymphoblastic lymphoma, as well as the role of radiotherapy in managing mediastinal disease. This case report highlights the limited evidence available regarding later-line treatments, with unusual reports regarding employing our combination of daratumumab and nelarabine, and emphasizes the importance of achieving cures in the first line of treatment.