Intravascular metastatic melanoma: a difficult diagnosis.

Melanoma is a common cancer with the potential for widespread metastasis; however intravascular metastasis is extremely rare. We report an unusual case of a patient with metastatic melanoma in whom (18) F-fluorodeoxyglucose positron emission tomography-computed tomography (FDG PET-CT) demonstrated an intravascular melanoma metastasis in the superior vena cava (SVC), successfully treated with external beam radiotherapy. To our knowledge, this is the first reported case where FDG PET-CT was used to make this diagnosis.