Follicular thyroid cancer avid on C-11 Methionine PET/CT

Summary A case of follicular thyroid cancer with intense focal Methionine uptake on 11C-Methionine PET/CT is reported here. The use of 11C-Methionine PET in differentiated thyroid cancer is currently being investigated as a surrogate tracer compared to the more widely used 18F-FDG PET. This case illustrates the potential incremental value of this modality, not only in the localizing of parathyroid adenoma, but also indicating that 11C-Methionine PET might have a potential of increasing the pretest likelihood of thyroid malignancy in a cold nodule with highly increased Sestamibi uptake. Learning points: 11C-Methionine PET/CT and 18F-Fluorocholine PET/CT often visualizes the parathyroid adenoma in case of negative Tc-99m-MIBI SPECT/CT. A cold nodule in Tc-99m Pertechnetat thyroid scintigraphy with a negative Sestamibi scintigraphy has a very low probability of being malignant. However, the pretest likelihood of thyroid cancer in a cold nodule with increased Sestamibi uptake is low. 11C-Methionine PET might have a potential incremental value in increasing the pretest likelihood of thyroid malignancy in a cold nodule with highly increased Sestamibi uptake.