Incidental thyroid nodule: patterns of diagnosis and rate of malignancy

Abstract 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.