Multiple Myeloma : Wheeless' Textbook of Orthopaedics

Discussion

myeloma is malignant tumor of plasma cells arising from a single clone;
multiple myeloma accounts for > 40% of primary malignant tumors of bone.
it is most common malignant primary tumor of bone
may arise as single intraosseous tumor but more often it develops as multiple painful lesions throughout skeleton (multiple myeloma);
whether from single or multiple sites, myeloma spreads to involve virtually entire bone marrow which eventually produces death;

normal marrow biopsy may show upto 8 % plasma cells;
between 10-20 % suggest myeloma;
greater > 20-30 % plasma cells on bx is diagnostic of myeloma;
immunohistochemical studies: may reveal lambda light chains or heavy chains and kappa light chains;

pts present in their middle fifties or older (60-70 yr)
constitutional symptoms, anemia, thrombocytopenia, and renal failure;
approx 80% of pts have chief complaint of bone pain w/ diffuse bone tenderness, particularly over the sternum and pelvis.
- pathological frx of spine or femur may be heralding event;
symptoms range in duration from as short as few wks to as long as 2 yrs.

standard x-rays may show diffuse osteopenia
"punched-out lesions" w/ no surrounding new-bone formation;
over time lesions may change from diffuse osteopenia to more permeative moth-eaten destructive pattern, sometimes w/ cortical expansion;
bone destruction occurs w/ little or no reactive bone formation unless pathologic frx is present;
bone scans:
- may or may not appear cold;
- bone-scanning, although likely to show incr activity at site of frx, shows no increase even at site of discrete lesion in 25 % of patients;
MRI:
- MRI of spine may show evidence of patchy areas, consistent with marrow element disease;
skeletal survey:
- skeletal survey is the most useful radiographic study to make the diagnosis;
- myeloma may present as solitary lesion or more commonly a diffuse tumor, involving multiple bones, including vertebrae, skull, pelvis and femurs;
- look for one fracture or more in the spine;
- sharply delineated punched-out lesions are seen best in skull;

myeloma is sensitive to XRT, & reossification of tumor defects may ocurr within several months.
XRT is recommended for intractable bone pain, esp if pain is localized;
it can be dramatically effective in relieving symptoms;