[The radiodiagnosis of bone metastases from melanoma]

The records of 3,795 cases of malignant melanoma treated at the INT (Milan) from 1975 to 1992 were reviewed. Histologic confirmation was obtained in all cases. Thirty-one patients (0.82%) with solitary or multiple skeletal metastases were identified. The review of conventional films, tomograms, CT, MR and bone scintigraphy images enabled us to detect 120 single bone lesions. The X-ray features were divided into two groups according to typical and atypical skeletal lesions. Typical bone metastases are osteolytic (87.5%), with medullary origin (91.6%), and they cannot be distinguished from other osteolytic metastases on the basis of imaging criteria alone. Lesion growth causes cortical erosion and destruction (46.6%), pathologic fractures (22.5%) and soft tissue involvement (12.5%). Lytic areas usually have ill-defined margins. Clear-cut outline is an uncommon finding. Atypical skeletal metastases exhibit a mixed osteolytic-osteoblastic pattern (10%), which is hardly ever completely osteoblastic (2.5%). Other unusual metastatic patterns include intense trabecular rarefaction with no detectable single lesion (3.3%), the presence of a well-defined sclerotic rim and periosteal reaction (12.5%). Atypical growth may cause extensive cortical destruction and periosteal production resembling osteogenic osteosarcoma. The various imaging methods show that conventional radiology has relatively poor sensitivity because of anatomical reasons, while MRI is the most sensitive method to detect skeletal localizations. Treatment changes the radiologic patterns of the lesions: recalcification, sclerotic rim, periosteal reaction are common response patterns. Finally, in spite of the above limitations, conventional radiology remains the method of choice to assess lesion evolution during the follow-up.