Friday, September 23, 2011

Melanoma Metastases to Bone

Skeletal metastases from malignant melanoma are found during autopsy in ~25% to 50% of patients who die of the disease. Radiolography and scintigraphy are much less sensitive, with metastatic lesions detected in less than 10% of patients. CT is slightly better, detecting axial skeletal metastases in about 15% of patients with melanoma.

Radiographic findings, when present, are nonspecific. Until cortical destruction has occurred, most medullary metastases are radiographically occult. Most skeletal metastases from melanoma progress rapidly. The vast majority of the lesions are osteolytic, although sclerotic or mixed lesions can also occur. The margins of the lesions are usually poorly defined. Periosteal reaction is uncommon, and when present, is minimal.

The CT findings in bony metastases from melanoma are nonspecific. The majority of lesions are osteolytic, slightly expansile, and occasionally associated with soft-tissue masses. The lesions may rarely be sclerotic, but tumor matrix is not generally seen in lytic lesions in the axial skeleton.

MRI findings are not as well described. A report of spinal metastases from melanoma described increased T1 signal intensity in bone.

The images above show an FDG-avid lytic lesion in the right side of the sacrum. As you can see, the lesion can be subtle, stressing the importance of careful evaluation of images in bone windows in these patients.


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