RESUMO
A 54 year old Japanese man was introduced to Saiseikai General hospital for an evaluation of an abnormal chest X-ray film. Abnormal soft tissue area was observed in the mediastinum surrounding anterior area of the trachea on chest CT. Because the mediastinal tumor showed slow enlargement after temporal decrease and surgical resection of the tumor was performed 3 years after the first visit. Pathologically, diffuse proliferation of oval-shaped plasmacytic or small lymphocytic cells with eccentrically-located nuclei with rough chromatin were observed in the tumor. Immunohistochemically, these cells were positive for CD20, weakly positive for IgM, negative for CD3, CD5, CD10, suggesting lymphoplasmacytic lymphoma (LPL). The patient was treated with rituximab after the surgical treatment, and showed no exacerbation for 3.5 years after surgery. LPL localized to the paratracheal mediastinum is rare, and a surgical approach is important for prompt and proper diagnosis.