Low-grade intraosseous osteosarcoma with prominent lymphoid infiltrate.

Low-grade intraosseous osteosarcoma is an uncommon and well-differentiated osteosarcoma with a good prognosis. We report a proximal tibial low-grade intraosseous osteosarcoma with a prominent intratumoral lymphoid infiltrate, which led to an initial diagnosis of probable malignant lymphoma. The importance of this infiltrate, which exhibited reactive features on flow cytometric studies, is not known. Our patient is free of tumor 1 year after limb salvage surgery, without hematologic or lymphoid abnormalities.