Clinicopathological correlation for the role of fluorodeoxyglucose positron emission tomography computed tomography in detection of choroidal malignant melanoma

Background: The purpose of this study was to redefine the role of whole-body 2-[¹⁸F]fluoro-2-deoxy-D-glucose (FDG) positron emission tomography fused with computed tomography (PET/CT) in the clinical diagnosis of choroidal malignant melanoma. Methods: The study design was a retrospective case series involving 7 consecutive patients with choroidal malignant melanoma who underwent enucleation to reach the final pathological diagnosis. FDG-PET/CT was performed together with magnetic resonance imaging and ophthalmological examinations before the surgery. The area, thickness, longest diameter, and circumference of the tumor mass were measured on pathological sections, and were correlated with maximum standardized uptake values (SUVmax) of the tumors on FDG-PET/CT. Results: Abnormally high uptake of FDG was noted in the affected eyes of 5 patients, but not in the eyes of 2 patients. The 5 patients with high uptake showed nodular tumors extruding into the vitreous cavity while the 2 patients with absence of uptake showed diffusely infiltrating tumors in the wide area of the choroid with or without a small mushroom-like protrusion. One patient with diffuse infiltration showed concurrent liver metastases with high uptake on PET/CT while another patient with a nodular tumor developed liver metastases a year later. The tumors with higher SUVmax had a tendency to have a wider area and greater thickness on pathological sections (ρ = 0.775, P = 0.0557, Spearman rank correlation test). Conclusions: FDG-PET/CT showed correlation of the uptake with tumor sizes but was limited in detecting diffusely infiltrating tumors in the choroid without nodular formation.