Objective To investigate the clinical value of ¹⁸F-FDG PET/CT imaging in detecting primary foci by analyzing images of squamous carcinoma patients with lymph node metastatic.

Methods A retrospective analysis was performed on 56 patients (44 males and 12 females, aged 19−81, with a median age of 51), who underwent whole-body ¹⁸F-FDG PET/CT for the diagnosis of metastatic squamous carcinoma with unknown primary foci during March 2018 to November 2020 at the Central Hospital of Chancheng District of Foshan City in Guangdong Province. Prior to imaging, the diagnosis of metastatic squamous cell carcinoma was confirmed by pathological examination in all patients, and the primary foci were confirmed by pathological examination or clinical follow-up. To analyze and calculate the detection rate of ¹⁸F-FDG PET/CT in the diagnosis of primary lesion and the relationship between primary lesion and lymph node metastasis and maximum standardized uptake value (SUV_max). SUV_max of primary tumor and lymph node metastasis were analyzed by bivariable correlation analysis.

Results Among 56 patients, 44 positive cases (42 true positive cases and 2 false positive cases) were detected by ¹⁸F-FDG PET/CT, with a detection rate of 75.0% and 1 false negative (nasopharyngeal carcinoma). Primary foci in 11 patients remained unfound by ¹⁸F-FDG PET/CT. The SUV_max of primary and metastatic foci were consistent to some extent (r=0.320, P<0.05).

Conclusion ¹⁸F-FDG PET/CT imaging has good clinical value for the detection of unspecified primary foci in metastatic squamous cell carcinoma, and there is a good correlation between the intensity of glucose metabolism in the primary foci and metastatic foci.