Incidental thyroid cancer detected by (18)F-FDG PET: does it have different clinicopathological features?

The prevalence and risk of malignancy in thyroid incidentalomas has been investigated in previous studies; however, these studies have not looked at the characteristics of incidental thyroid cancer (ITC) detected by fluorine-18 fluorodeoxyglucose PET. Therefore, we aimed to assess the clinicopathologic features of ITC.

From March 2008 to December 2011, a total of 2892 patients underwent total thyroidectomy for papillary thyroid cancer. Among them, patients belonging to the ITC group were defined as those in whom focal thyroid uptake was reported as an incidental finding on PET imaging and further evaluation revealed the presence of malignancy. In addition, two control groups with non-PET incidental thyroid cancer (NITC) were selected: NITC-A patients (n=48) who underwent a total thyroidectomy in March 2008 and NITC-B patients (n=48) who underwent a total thyroidectomy for papillary thyroid cancer and were matched for the confounding effects of age and sex.

There were no significant differences in clinicopathologic features, except for age and tumour node metastasis (TNM) staging, between ITC and NITC-A patients. More ITC than NITC-A patients were aged 45 years or older. Although T, N, or M staging was not different between ITC and NITC-A, there were more ITC patients with stage III/IV tumours. After matching for age and sex, none of the clinicopathologic features showed significant differences between ITC and NITC-B patients.

No significant differences were observed between ITC and NITC patients except for age and TNM staging. More ITC patients had advanced TNM stage most likely due to patient age.