[Whole-body staging of malignant melanoma: advantages, limitations and current importance of PET-CT, whole-body MRI and PET-MRI].

Cross-sectional imaging methods are currently the standard methods for staging of advanced melanoma. The former time-consuming and expensive multimodality approach is increasingly being replaced by novel whole-body (WB) staging methods, such as 18F-fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG-PET-CT) and whole-body magnetic resonance imaging (WBMRI) because they offer a complete head-to-toe coverage of the patient in a single examination with an accurate and sensitive detection of tumor spread. Several studies in patients with advanced melanoma revealed that PET-CT is more sensitive and specific than conventional modalities, such as CT alone resulting in a change of management in up to 30 % of cases. Due to the limited sensitivity of PET for lesions smaller than 1 cm, PET-CT is not useful for the initial work-up of patients with stage I and II melanoma but has proven to be superior for detection of distant metastases, which is essential prior to surgical metastasectomy. If PET-CT is not available WB-CT or WB-MRI can alternatively be used and WB-MRI including diffusion-weighted imaging (DWI) has become a real alternative for staging of melanoma patients. So far, however, only few reports suffering from small numbers of cases and heterogeneous design have compared the diagnostic performance of WB-MRI and PET-CT. The preliminary results indicate a high overall diagnostic accuracy of both methods; however, these methods differ in organ-based detection rates: PET-CT was more accurate in N-staging and detection of lung and soft tissue metastases whereas WB-MRI was superior in detecting liver, bone and brain metastases. The value of PET-MRI for staging of advanced melanoma is the subject of ongoing clinical studies.