Primary bone lymphoma in a 10-year-old boy.

Primary bone lymphoma has been defined as a solitary lesion in bone, without concomitant involvement of the extra osseous hematopoietic system, with no evidence of extra osseous disease within 6 months of the onset of symptoms. The vast majority of cases are of the large B-cell non-Hodgkin type. They are rare bone tumor. Distinguishing primary bone lymphoma from other bone tumors is important because the former has a better response to therapy and a better prognosis.