Glucose metabolism and pathological findings in uveal melanoma

The aims of this study were to assess the sensitivity of positron emission tomography (PET) using [18F]fluorodeoxyglucose (18F-FDG) in the detection of uveal melanoma, and to establish the relationship between pre-operative 18F-FDG uptake and a number of pathological features of uveal melanoma. Twenty consecutive patients with a clinical diagnosis of uveal melanoma were enrolled in the study. 18F-FDG uptake was assessed in all subjects and the following parameters were assessed in 11 enucleated subjects: the mitotic index, the MIB-1 proliferating cell index, number of epithelioid cells, largest tumour diameter, tumoral necrosis and inflammatory infiltration. Tumours with a diameter less than 7.5 mm were not detected by PET, possibly because of limited spatial resolution, and only 7 of 12 tumours with a diameter greater than 7.5 mm were detected. With tumours greater than 7.5 mm in diameter, PET and 18F-FDG allow two subgroups to be distinguished: those with high and those with low glucose consumption. Apart from tumour size, 18F-FDG uptake was not related to the pathological features examined. We hypothesize that 18F-FDG uptake may be related to the ratio of viable to non-viable cells, or to the hypoxic cell fraction within the tumour.