PET/CT in Melanoma (Additional Teaching Cases)

Abstract

In this pictorial review chapter, we present a series of cases highlighting the utility of nuclear medicine in melanoma management and outline some important pitfalls. We highlight the ability of SPECT/CT to demonstrate atypical drainage pathways that are difficult to identify on conventional planar imaging. Whilst SPECT/CT enables precise localisation of sentinel nodes, there is reduced sensitivity near the site of injection owing to flare of activity which may result in false-negative findings. For PET/CT, we demonstrate the high sensitivity of PET to detect sub-centimetre metastases, and its essential application prior to surgical intervention to accurately stage the patient and also the ability to differentiate postsurgical changes from recurrent disease. We show examples of immune related inflammatory effects visualised on FDG PET/CT that should not be misinterpreted as malignant in aetiology. Although not directly an immunotherapy like CTLA-4 or PD-1 pathway blockade, features of an immune-related inflammatory response such as reactive nodal activity or diffuse splenic activity are also seen with BRAF inhibitors. We also highlight how early identification of metastatic melanoma with imaging may not change survival but cause morbidity from consequences of additional interventions. In the setting of oligometastatic disease, a short period of observation with repeat imaging to ascertain rate of temporal change and metastatic progression can be a useful approach to reduce futile interventions. With availability of newer therapies, however, the treatment landscape continues to evolve.