SpineTF11-Multiple Myeloma

Clinical Profile:

C/O right sided girdle pains. Patient has received six rounds of chemotherapy

Findings:

There is a lesion involving the D9 spinous process, pedicles and laminae with compression upon the spinal cord. The lesion shows intermediate signal characteristics on theT1W images & is slightly hypointense on the T2W images. Also seen are lesions in the right sacral ala and iliac bone and in the S3 vertebral body.

Discussion: 

Multiple myeloma (MM) is a malignant disease of plasma cells that usually originates in the bone marrow but may involve other tissues as well. Solitary plasmacytoma/myeloma (SM) may be a distinct entity. However, they are most likely an early manifestation of MM with classical MM developing later (even 5 to 10 years later). It is the most common primary bone tumor, accounting for 1% of all malignancies and 15% of hematologic malignancies. SM is seen in 3-5% of cases of myeloma.

MM usually involves the spine, ribs, pelvis, skull and long bones, while involvement of small bones is rare. The dorsal and lumbar regions are more commonly involved. The vertebral bodies are more commonly involved than the pedicles (paucity of red marrow). Later on there is conversion of yellow to red marrow with involvement of the pedicles and posterior elements. Extramedullary plasmacytomas without bone involvement is seen in 3-5% of cases (80% involving the upper airways).

Patients usually present with pain in the region of involvement. They may have weakness and weight loss. Fractures of the ribs and vertebrae may be seen. They may also present with symptoms related to spinal cord or nerve root compression. Patients may develop purpura or epistaxis. Renal involvement is known (amyloid deposition)
Sclerotic lesions may be associated with the POEMS syndrome.

• Polyneuropathy

• Organomegaly

• Endocrinopathy

• M protein elevation

• Skin lesions
   

Pathology:

Grossly, the marrow is replaced by poorly defined confluent small tumor nodules, that are dark red or brown in colour. On H/P there are sheets of cells with basophilic cytoplasm and sparse stroma. The myeloma cells are larger than the plasma cells.
M component is found in urine/serum of 99% of patients. They usually have normochromic, normocytic anemia. The WBC count prior to treatment is near normal. The platelets may be decreased, there may be hypercalcemia and the ESR is elevated.

Imaging:

On MRI, four patterns of involvement may be seen:

• Normal marrow signal - 31%

• Discrete focal lesions - 31%

• Diffuse marrow involvement - 24%

• Inhomogeneous marrow pattern due to multiple tiny areas of marrow involvement (variegated) - 14%

The lesions are usually hypointense on T1W images and turn hyperintense on T2W and STIR images. Very rarely the lesions may be hyperintense on the T1W images due to hemorrhage. 2% of the lesions are sclerotic. Compression fractures are commonly encountered in the spine. The lesions usually enhance after contrast (gadolinium) administration. SM usually shows dense enhancement. Meningeal enhancement is seen with thecal sac involvement. CSF may be positive for plasma cells in such cases. Lesions are usually treated with chemotherapy and/or localized/total body radiation. Following treatment the lesions may be hypointense on all pulse sequences (probably due to fibrosis). The treated lesions only enhance mildly.

CT is less sensitive than MRI. However, it is useful to look for calcium in the lesions which could narrow the differential diagnosis. MRI is useful as a screening tool.

Plain radiographs may demonstrate punched out lesions (usually in the skull), expansile lesions or generalized osteopenia. With severe osteolysis the lesions may have a soap bubble or reticulated appearance.

 Radionuclide scintigraphy, although sensitive to most metastatic processes, is notoriously unreliable in patients with multiple myeloma. It is positive in only 20% of cases. Cold lesions are seen in 5% of the cases.

Differential Diagnosis:

Diffuse Hypointense Lesions On T1W Images:

• Marrow reconversion, from yellow to red
   

• Marrow replacement

  • Myelofibrosis

  • Myeloproliferative syndromes like lymphoma or leukemia

  • Extensive metastasis

  • Gaucher's disease

  • Primary amyloidosis

  • Iron overload

  • Infections (especially in immunocompromised individuals)

  • Hematopoietic disorders

Focal Lesions:

• Metastasis

• Lymhoma

• ABC

• GCT

• Osteoblastoma

• Osteoid Osteoma

• Ewing's sarcoma

ABC, osteoblastoma and osteoid osteoma usually involve the posterior elements. GCT, hemangioma and metastasis usually involve the vertebral body. Calcium may be seen in chordoma, chondrosarcoma and osteoblastoma.