Characteristics of Breast Cancers with Concurrent Focal Thyroid Incidentalomas Using <sup>18</sup>F-Fluorodeoxyglucose Positron Emission Tomography

Abstract

Purpose: The aim of this study was to compare the incidence of focal thyroid incidentalomas on F-fluorodeoxyglucose positron emission tomography/computed tomography (F-FDG PET/CT) in breast cancer patients with the incidence in healthy women, and to assess for any significant characteristics of the breast cancers in patients with concurrent focal thyroid incidentalomas. Methods: We retrospectively reviewed the medical records of 489 breast cancer patients and 286 healthy women who were evaluated with F-FDG PET/CT between March 2010 and February 2012. We analyzed the images visually and obtained semiquantitative indices. Results: The overall incidence of focal thyroid incidentalomas was 9.4% (46/489) in breast cancer patients and 5.9% (17/286) in healthy patients (p<0.01). Among 23 focal incidentalomas in breast cancer patients and five in healthy women with additional cytological and histological diagnoses, papillary thyroid carcinoma was diagnosed in 11 breast cancer patients (23.9%) and in two healthy patients (11.7%). Ductal carcinoma in situ (p=0.03), estrogen receptor (ER) positivity (p<0.01), progesterone receptor (PR) positivity (p<0.01), and Ki-67 positivity (p<0.01) were correlated with breast cancer patients with focal thyroid incidentalomas. Conclusion: Focal thyroid incidentalomas were more frequently detected with FFDG PET/CT in patients with breast cancer than in healthy women. Focal thyroid nodules incidentally found with F-FDG PET/CT in breast cancer patients have a high risk of malignancy. ER positivity, PR positivity, Ki-67 positivity, and ductal carcinoma in situ correlated positively with F-FDG PET/CT-detected focal thyroid incidentalomas.