Primary bone malignant lymphoma: radiographic and magnetic resonance images.

A 70-year-old man with a 3-month history of low back pain was admitted to our hospital due to difficulty in walking with pain and swelling in the right knee joint in September 2004. On admission, physical examination revealed a 15 cm mass with fever in the right knee joint. The superficial lymph nodes were not enlarged. The erythrocyte sedimentation rate and soluble interleukin 2 receptor level were 92 mm/h and 977 U/ml, respectively. However, the levels of other tumor markers and immunoglobulin were normal. In the radiography, permeative and moth-eaten bone destruction with pathological fractures in the distal femur was observed (Fig. 1). Magnetic resonance (MR) imaging showed marrow replacement and surrounded by a soft tissue mass in the distal femur (Fig. 2A, B). An open biopsy of the tumor demonstrated proliferation of abnormal lymphoid cells. Immunohistochemical staining revealed that the biopsy specimens were positive for CD20, CD 79a and CD5, which are surface markers of B cell lymphocyte (Fig. 3A, B). Other surface markers for T cell lymphoma,