Primary lymphoma of bone in the pediatric and young adult population.

Primary lymphoma of bone (PLB) accounts for 3% to 7% of primary neoplasms of bone and must be distinguished from more common bone tumors in the pediatric population such as osteosarcoma, Ewing sarcoma, and other small round blue cell tumors. In this study, pathology databases from 4 institutions were queried for PLB in individuals 1 to 21 years old. A total of 54 cases of PLB were identified, including 41 diffuse large B-cell lymphomas (DLBCL, 76%), 8 B-lymphoblastic lymphomas (BLL, 15%), 3 anaplastic large cell lymphomas (ALCL, 6%), and 2 low-grade follicular lymphomas (4%). The male/female ratio was 1.8:1 and median age was 16 years (range, 2-21). Patients with DLBCL were significantly older (P<.001), and patients with ALCL and BLL were significantly younger (P=.050 and P=.008, respectively) when compared with the other patients. Due to necrosis, crush artifact, and/or insufficient material, 30% of cases required multiple biopsies for diagnosis. The femur, tibia, pelvic bones, humerus, and vertebrae were most commonly involved. DLBCL patients had significantly more solitary bone involvement (P=.001), whereas BLL had significantly more polyostotic involvement (P<.001). Of the 37 patients with outcome data, all had no evidence of disease on last follow-up. This largest pediatric series of PLB identifies DLBCL as the most frequent subtype and documents rarer occurrences of BLL, ALCL, and follicular lymphomas. The differential diagnosis of bone neoplasms in pediatric patients, including those with necrosis, should include PLB.