Metastases from malignant melanoma to the axial skeleton: a CT study of frequency and appearance

Radiologic detection of bone lesions from malignant melanoma is reported to be uncommon or infrequent. To ascertain the characteristics and frequency of detection of melanoma metastases to the axial skeleton by CT, we retrospectively reviewed 464 body CT studies of 125 consecutive melanoma patients for presence, appearance, and site of skeletal metastases. Results were correlated with patient's age, sex, clinical course, and both the Clark and Breslow classifications of the primary lesion. Of 98 patients with metastatic disease evident on their CT studies, 17 (17%) had bony metastases; two (12%) of these 17 patients had skeletal lesions as the only CT evidence of metastatic disease. Metastatic bony lesions were predominantly osteolytic, slightly expansile, and commonly located in the spine. Associated soft-tissue masses were frequent, but periosteal reaction and identifiable tumor matrix were not seen. Skeletal metastases were found only in those patients with thick or intermediate primary melanoma (Breslow) classified as Clark level III or greater, and the CT demonstration of osseous metastases was a poor prognostic sign. The data suggest that CT detection of skeletal melanoma metastases is not uncommon. When CT is performed to evaluate for metastatic melanoma, the axial skeleton should be carefully examined, especially in those patients with more advanced primary lesions.