Multiple Myeloma

This is not a subtle case -- destruction is widespread and obvious. Close inspection

of the largest lesion shows it to be purely lytic, without any matrix or calcification. There are numerous "tear-drop" shaped lytic lesions in the

left femur. Pathologic fracture of the neck of the femur can be clearly seen.

For all practical purposes, the differential diagnosis is between Multiple Myeloma (MM) and metastatic disease, especially breast in a female. While one cannot usually decide between MM and lytic metastases, there are some helpful clues:

MM is often associated with hypercalcemia.
MM often has a positive serum and/or urine electrophoresis.
MM is only EXTREMELY RARELY sclerotic.
MM is more likely to affect a vertebral BODY while metastatic disease is more likely to involve the PEDICLE.
- A different patient with MM and spinal involvement shows compression fracture of a myelomatous L5 vertebra.
MM often shows characteristic "punched out" lytic lesions in the skull.
However, as these lesions in the humerus show, it is frequently impossible to distinguish between MM and lytic metastases.

There are some additional points that "come up in conversation" -- e.g., in Louisville during the Radiology Oral Boards!

Older age groups (age 40-80). M>F. More common in black people.
Death usually from infection, renal failure.
MM can present as diffuse osteopenia, thus simulating osteoporosis.
X-ray bone surveys often preferred to bone scans which can miss lesions.
When lesion is solitary, it is termed plasmacytoma. It may or may not progress to MM.
Sclerotic lesions associated with P(polyneuropathy)O(organomegaly) E(endocrinopathy)M(-protein)S(kin changes) Syndrome.
Amyloidosis occurs in 15% of patients.
- Calcification within MM lesion is due to amyloid and can simulate chondrosarcoma.

Ref:Resnick, D., Bone and Joint Imaging, W.B. Saunders, Philadelphia, PA., 1989, pp. 675-682.

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