Incidental thyroid nodule: patterns of diagnosis and rate of malignancy

BACKGROUND: The clinical significance of thyroid incidentalomas is controversial. METHODS: The rate of malignancy was determined for patients with an incidentally discovered thyroid nodule, and results were stratified according to imaging modality as well as presence and type of pre-existing malignancy. RESULTS: One hundred fifty patients were identified, of which 88 with a known malignancy were screened for metastases. Twenty-three (15%) patients were diagnosed with thyroid malignancy Incidental nodules identified on positron emission tomography scan were malignant in 33% of the patients compared with 11% for those identified on computed axial tomography (P=.016). The rate of thyroid malignancy in patients with pre-existing nonthyroid malignancy(18%) was not significantly different from patients without a history of malignancy (13%, P = .36). COMMENTS: Thyroid incidentalomas are associated with a high rate of malignancy. The rate of malignancy is highest for nodules discovered on positron emission tomography scan and is no different in patients with or without pre-existing malignancy. (C) 2009 Published by Elsevier Inc.