Primary lymphoma of the bone


 * Associate-Editor-In-Chief: John Fani Srour, M.D.

Overview
Primary lymphoma of the bone (PLB) is an uncommon malignancy that accounts for less than 5% of all primary bone tumors. The majority of cases are of the non-Hodgkin type, with Hodgkin disease accounting for 6% of cases.

Peak prevalence
The peak prevalence is among patients in the 6th to 7th decades of life.

Forms
The presence of a solitary metadiaphyseal lesion with a layered periosteal reaction on plain radiographs and a soft-tissue mass on MRI is highly suggestive of lymphoma. However, diffuse multifocal osseous involvement and variable radiographic appearances of primary bone lymphoma are well known features.

Most common sites
The femur is the most common site and is affected in 25% of cases. Vertebral involvement is not unusual.

Groups
Although the original criteria for PLB described by Coley implied the involvement of a solitary bone, an expansion was suggested by Ostrowski et al in 1986 when they sub-classified osseous lymphoma into four groups. Group 2 includes cases in which more than one bone was affected but no nodal or visceral disease was present.

Clinical manifestaions
Primary lymphoma of bone manifests with insidious bone pain, local swelling, a palpable mass, and systemic symptoms such as weight loss and fever. Vertebral involvement can cause radicular symptoms and, in some case, lead to compression of the spinal cord.

Pathology
PLB most commonly are large cell or mixed small and large cell lymphomas of the B-cell lineage. On the basis of the current WHO classification, the majority of cases would be characterized as diffuse large B-cell lymphoma. T-cell primary bone lymphomas are rare and almost all lymphomas will express common leukocyte antigen and B-cell markers CD20 and CD79a.

Imaging
The radiographic appearances of PLB are variable, and because the lesion can appear near normal on plain radiographs, bone scan or magnetic resonance imaging (MRI) should be used.

Treatment
Treatment for PLB often involves radiation therapy to control the tumor in the affected bone. In certain instances, surgical intervention for control of the primary bone lesion may be desirable or necessary. Chemotherapeutic regimens are employed in cases of diffuse osseous involvement.

Prognosis
Distinguishing primary bone lymphoma from other bone tumors is important because PLB has a better response to therapy and a better prognosis.