Review Question - QID 219346

The patient has primary bone lymphoma (PBL), which stains positively on immunohistochemical stains for CD20 and CD45.

Primary bone lymphoma (PBL) is relatively rare, accounting for only 2 to 3% of all primary bone malignancies. It presents most typically in patients between the ages of 35 and 55 with regional pain and the "B symptoms" of fevers, night sweats, and unexplained weight loss. Radiographs may be unremarkable and show minimal bone destruction, but MRI often shows a large soft tissue mass out of proportion to the amount of representative bony destruction (Figure A). Diagnosis is made with a biopsy showing a mixed small round blue cell infiltrate (Figure B), with immunohistochemistry showing CD20+ and CD45+ cells. Patients with symptomatic bone lesions are at risk for pathologic fracture and should be prophylactically stabilized, followed by appropriate chemotherapy.

Ramadan et al. provide a clinicopathological retrospective study of 131 patients with primary bone lymphoma. The authors noted that patients with diffuse large B-cell lymphoma (DLBCL) had 5- and 10-year overall survivals (OS) of 62% and 41%, respectively, with neither primary site nor pathological fracture at presentation impacting overall survival. The 3-year progression-free survival in patients who received rituximab plus combination chemotherapy with cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOPR) chemotherapy was 88%, compared with 52% in those who received CHOP-like chemotherapy without rituximab. They concluded that PBL is usually DLBCL type and has an improved outcome with CHOPR.

Bruno et al. published the clinical features, management, and prognosis of an international series of 161 patients with limited-stage diffuse large B-cell lymphoma of the bone (PB-DLBCL). The authors' primary objective of the study was to identify the most effective treatment modality, with the secondary aim of defining the contribution of irradiation fields and doses to the patterns of relapse. They concluded that patients with PB-DLBCL exhibit a favorable prognosis when treated with primary anthracycline-based chemotherapy, whether followed by radiotherapy or not.

Lewis et al. published on the oncologic outcomes of primary lymphoma of bone in adults. The authors retrospectively reviewed 28 patients and found a 5-year Kaplan-Meier survival estimate of 57.8%, with statistically improved survival seen in patients younger than 40 years and in patients with diffuse large B cells with multi-lobulated nuclei. They concluded that age at diagnosis and histologic subtypes are important prognostic factors.

Figure A represents a coronal MRI, STIR sequence showing a diaphyseal tibial lesion with a large soft tissue component. Figure B is a biopsy slide showing diffuse, small, round blue cells consistent with lymphoma.

Incorrect Answers:
Answer 2: CD31 and CD34 stain positively in tumors of endothelial cell/vascular origin (i.e., hemangiomas, hemangioendotheliomas, and angiosarcomas).
Answer 3: CD99 and FLI-1 stain positively in Ewing Sarcoma, which would be highly unlikely in a 50-year-old of the given presentation.
Answer 4: CD138 stains positively in myelomas, typically showing "punched-out" bony lesions on radiographs and a mild zone of soft tissue edema on MRI, not a large concomitant soft tissue mass, as in this patient.
Answer 5: Desmin and MyoD1 stain positively in rhabdomyosarcomas, which occur more frequently at ages <30 and show large soft tissue masses without bony involvement.