Staging of cutaneous malignant melanoma by CT

Malignant melanomas are a challenge in radiological imaging diagnostics as they may metastasize into every organ and tissue. Cross-sectional imaging, in particular positron emission tomography computed tomography (PET/CT) and whole body magnetic resonance imaging (MRI), are considered the standards in the staging of melanomas. Because of its excellent availability CT, however, remains a widely employed staging modality. Familiarity with the manifold CT morphology of metastasized melanomas as it is described here is essential when interpreting dedicated CT and in addition useful when interpreting PET/CT results. In individual cases CT can assist in the detection of transient metastases. In the detection of locoregional lymph node metastases CT has a median sensitivity and specificity in meta-analyses of at best 61 % and 97 %, respectively, which is inferior to the performance of ultrasound (96 % and 99 %, respectively). According to meta-analyses, in the assessment of systemic tumor spread CT can detect the majority of metastases with a sensitivity and specificity of 51-63 % and 69-78 %, respectively, which is inferior to MRI and PET/CT. Therefore, if an exact staging is required for critical management decisions, MRI or PET/CT should be employed whenever possible.