Multiple Myeloma

Multiple myeloma is the most common primary malignant disease to involve bone. This abnormal proliferation of cells involves the marrow space and has a varity of imaging findings, which vary per modality. Imaging with plain film, CT, MRI, Bone Scan and recently PET can all play a complimentary role.
Plain films can show lytic lesions however may only show osteopenia. Given that individuals, who at greastest risk are elderly, this may be confused with senile osteoporosis.

CT has greater sensitivity to endosteal erosions however is often limited to aa single body part and has risk of increased exposure to ionizing radiation.

MRI is an excellent modality for marrow space involvement but again is limited by field of view.
Bone scan findings are nonspecific however range from normal, to increased activity with associated fracture, or the difficult "cold" lesion.

Recently PET has shown promise as an imaging technique. While not approved for multiple myeloma, entire/whole body imaging can be performed and may have increased sensitivity.

Note: additional findings are addressed in other factoids on this site.