musculoskeletal and connective tissue disorders
Primary Malignant Bone Tumors
Multiple myeloma
Multiple myeloma is the most common primary malignant bone tumor but is often considered a marrow cell tumor within the bone rather than a primary bone tumor because it is of hematopoietic derivation (see also Multiple Myeloma ). Even if multiple myeloma is considered a hematologic tumor, the identified skeletal abnormality must be differentiated from other bone tumors. Multiple myeloma occurs mostly in older adults. Tumor development and progression is usually multicentric and often involves the bone marrow so diffusely that bone marrow aspiration is diagnostic. Unlike in metastatic disease, a radionuclide bone scan may not reliably show lesions and skeletal surveys should be done. Skeletal surveys typically show sharply circumscribed lytic lesions (punched-out lesions) or diffuse demineralization. Rarely, the lesion can appear as sclerotic or as diffuse osteopenia, especially in a vertebral body. An isolated single myeloma lesion without systemic marrow involvement is called a plasmacytoma. Certain bony lesions respond quite well to radiation therapy. 