Noij DP, et al. - In patients presenting with nodal metastasis of an unknown primary head and neck squamous cell carcinoma (HNSCC), researchers evaluated the diagnostic value of DWI and ¹⁸F-FDG-PET/CT for detecting primary tumors via 31 patients presenting with a pathologically proven cervical nodal metastasis from HNSCC without an evident primary tumor location between January 2013 and November 2016 and underwent both DWI and ¹⁸F-FDG-PET/CT. The results obtained from this retrospective study indicate that the diagnostic accuracy of DWI and ¹⁸F-FDG-PET/CT were high in occult HNSCC. However, the accuracy of ¹⁸F-FDG-PET/CT was not improved with the addition of DWI. Study findings suggested that, with the current diagnostic approach, some primary tumors remain occult.