A rare collision tumor of lymphoepithelioma-like carcinoma and t-cell lymphoma: a case report.

We report a rare case of a collision tumor in a patient concurrently diagnosed with lymphoepithelioma-like carcinoma (LELC) and T-cell non-Hodgkin lymphoma (NHL-T). The patient was a 61-year-old male presenting with a one-week history of low back pain. Positron emission tomography-computed tomography (PET-CT) revealed hypermetabolic masses in the anterior mediastinum, adjacent to right cardiophrenic angle, in the retroperitoneum, and adjacent to the left iliac vessels in the pelvis. The puncture biopsy of the mass adjacent to the cardiophrenic angle suggested LELC coexisting with NHL-T. The patient was treated with a combination regimen of a PD-1 inhibitor and platinum-based chemotherapy, but disease progression was observed. Subsequent biopsy of the pelvic mass confirmed the presence of NHL-T. The treatment regimen was then modified to include a PD-1 inhibitor, bortezomib, and ICE (ifosfamide, carboplatin, etoposide) chemotherapy. After two cycles, the response was assessed as partial remission. The patient remains on ongoing therapy. This case highlights diagnostic challenges and provides insights into the management of such rare collision tumors.