Differentiation of synchronous primary tumors through the discrepancy in intensity of [¹⁸F]FDG uptake: Two case reports

Document Type : Case Report

Author

Department of Nuclear Medicine, Inje University College of Medicine, Ilsan Paik Hospital, Goyang, Republic of Korea

Abstract

Synchronous primary tumors (SPTs) refer to the pathologically different tumors coexisting in an individual. This phenomenon is often identified during cancer evaluation using [18F]fluorodeoxyglucose positron emission tomography/computed tomography ([18F]FDG PET/CT). The two cases presented here highlight discrepancies in [¹⁸F]FDG uptake intensity between the SPTs. Case 1 features a breast cancer with high uptake and a second primary lung cancer with low uptake, while Case 2 describes an esophageal cancer with low uptake and an incidental paraganglioma with high uptake. [¹⁸F]FDG uptake varies by histopathological characteristics and is typically consistent within the same clonal group. A lesion showing discordant uptake relative to the primary tumor on [¹⁸F]FDG PET/CT may indicate another distinct tumor.

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