The relationship between histopathological findings in oral squamous cell carcinoma and FDG uptake on PET

It is known that, in fluorine-18 fluorodeoxyglucose positron emission tomography (FDG PET) for the diagnosis of oral cancer, FDG uptake may vary even among different cases of the same squamous cell carcinoma. However, the details of this phenomenon have not yet been elucidated. In this study, we analyzed the relationship between histopathological findings in oral squamous cell cancer and PET findings on FDG uptake. We examined 45 patients with oral squamous cell carcinoma who had undergone FDG PET before treatment. FDG uptake was assessed by a standardized uptake value (SUV) calculated according to the PET-measured tissue concentration of FDG, the administered dose of radionuclide, and the body weight of the patient. The relationship between the mean SUV and each of the following parameters was examined: histological grade of malignancy, degree of cell differentiation, size and/or local extent of the primary lesion, and cell density of the tumor. The mean SUV of FDG uptake did not depend on the histological grade of malignancy or on the degree of cell differentiation, but tended to be greater the larger the primary lesion. SUV also depended on cell density, increasing with the percentage of tumor parenchyma. It is concluded that cancer cell density greatly influences the SUV of FDG, in that a tumor with fewer cellular elements in cancer tissue tends to become a false negative. (author)