Role of PET/MRI in oral cavity and oropharyngeal cancers based on the 8th edition of the AJCC cancer staging system: a pictorial essay

The American Joint Committee on Cancer (AJCC) released the 8th edition of the AJCC cancer staging manual in 2017 that includes significant modifications from the 7th edition in the sections on oral cavity cancer (OCC) and oropharyngeal cancer (OPC). These highlights comprise the incorporation of the depth of invasion and exclusion of extrinsic tongue muscle involvement in the T staging of OCC, the separation of OPC staging based on the high-risk human papilloma virus status, and the inclusion of extranodal extension in N staging. The recent introduction of integrated positron emission tomography and magnetic resonance imaging (PET/MRI) with 2-[F-18]-fluoro-2-deoxy-d-glucose (F-18-FDG) has demonstrated the advantages of simultaneous PET and MR imaging with higher soft-tissue contrast, multiplanar image acquisition, and functional imaging capability. This pictorial essay discusses the role of F-18-FDG PET/MRI in the diagnosis of OCC and OPC based on the new cancer staging system.