Thyroid incidentalomas are nonpalpable, asymptomatic thyroid nodules that are discovered on an imaging study performed to evaluate other structures or during an operation unrelated to the thyroid gland. Thyroid incidentalomas are most commonly detected on ultrasound (US) performed for evaluation of extra-thyroidal structures, followed in frequency by computed tomography (CT), magnetic resonance imaging (MRI), and
fluoro-2-deoxy-d-glucose (FDG)-positron emission tomography [PET] (
FDG-PET). Clinically unrecognized thyroid nodules are common and can be found in up to 50–60% of patients at autopsy. Increased use of imaging modalities of better quality in the modern era has resulted in an increased detection of incidental thyroid nodules. Their clinical importance is primarily related to the need to exclude thyroid cancer. The risk of malignancy in these nonpalpable nodules is similar to that of palpable nodules. As result, a thorough sonographic evaluation of the thyroid gland should be performed in the majority of patients with a thyroid incidentaloma. If a thyroid nodule is confirmed, then it should be evaluated in the same fashion as a clinical apparent thyroid nodule. As with most thyroid nodules, the majority will prove to be benign. However, as more studies come into light, we come to realize that the majority of incidental thyroid nodules that harbor cancerous cells are small indolent papillary carcinomas that do not result in increased mortality, and in such cases, a less aggressive and cost-effective approach is advised.