Head and neck cancers. Place of the imaging modalities

Most of head and neck tumors are squamous cell carcinoma for which FDG uptake is always present and thus which may he explored with that technique, beyond conventional imaging, CT and MR. In initial work-up of these tumors, morphologic imaging is essential, the role of FDG-PET being limited, except for some small lesions, especially sub-mucous lesions sometimes hard to individualize. Both techniques are complementary, for lymph node staging; FDG:-PET is able to identify small involved nodes whereas necrotic nodes, obvious in conventional imaging, may be missed by that technique. FDG-PET performed in adjunct to conventional imaging is contributive to identify distant metastases and/or second primary, In work-up of cervical adenopathies of unknown primary, PET should be performed following negative conventional imaging, the additional value of PET in that issue being reported in various ways probably due to lack of available data. In assessment of response to therapy, experience regarding additional value of PET compared to conventional imaging is insufficient; the functional nature of information obtained from PET is of interest but the specificity of abnormalities observed immediately following therapy is low. For follow-up, either one or the other approach will he chosen depending on the context; in that issue, strong point of PET is represented by its high negative predictive value regarding the diagnosis of recurrent disease. Thus, on the whole, morphologic and functional approaches are especially complementary in time management of head and neck tumors. (authors)