From the Guidelines
A thyroid ultrasound to check for cancer is recommended when a patient has a thyroid nodule larger than 1 cm, or when nodules have suspicious features on physical examination or ultrasonographic suspicion of malignancy, as indicated by the most recent and highest quality study 1. When evaluating the need for a thyroid ultrasound, several factors should be considered, including the size of the nodule, patient's age, and clinical or ultrasonographic suspicion of malignancy. According to the study by 1, thyroid nodules are common, but thyroid cancer is rare, accounting for only 5% of all thyroid nodules.
- The study 1 suggests that fine needle aspiration cytology (FNAC) should be performed in any thyroid nodule larger than 1 cm and in those smaller than 1 cm if there is any clinical or ultrasonographic suspicion of malignancy.
- The results of FNAC are very sensitive for the differential diagnosis of benign and malignant nodules, although there are limitations, such as inadequate samples and follicular neoplasia, as noted in the study by 1.
- Measurement of serum calcitonin is a reliable tool for the diagnosis of medullary thyroid cancer, which accounts for 5-7% of all thyroid cancers, and has higher sensitivity compared with FNAC, as indicated by the study 1.
- The initial treatment of differentiated thyroid carcinoma (DTC) should always be preceded by careful exploration of the neck by ultrasound to assess the status of lymph node chains, as recommended by the study 1.
- The study by 1 highlights the importance of imaging in the management of thyroid cancer, including operative planning, routine tumor surveillance, and further evaluation of suspected recurrence.
- It is essential to consider the potential risks of overdiagnosis and overtreatment of thyroid cancer, as noted by the study 1, which estimates that "overdiagnosis" accounts for 77% of thyroid cancer cases in the United States.
From the Research
Indications for Thyroid Ultrasound
- A palpable mass on clinical examination 2
- Abnormality of thyroid function tests 2
- Incidental finding on other imaging modalities, such as nuclear scintigraphy or computed tomography scan 2
- Screening for patients with risk factors for malignancy, such as multiple endocrine neoplasia type II 2
- Prior neck radiation treatment 2
Ultrasound Characteristics Associated with Thyroid Cancer
- Microcalcifications (odds ratio [OR], 8.1; 95% CI, 3.8-17.3) 3
- Size greater than 2 cm (OR, 3.6; 95% CI, 1.7-7.6) 3
- Entirely solid composition (OR, 4.0; 95% CI, 1.7-9.2) 3
- Solid structure, hypoechogenicity, irregular margins, absence of halo, microcalcifications, central vascularization, solitary nodule, heterogeneity, taller than wide shape, and absence of elasticity 4
Thyroid Imaging Reporting and Data System (TI-RADS)
- A standardized approach to classifying nodules on ultrasound 5
- Categorizes nodules as benign, minimally suspicious, moderately suspicious, or highly suspicious for malignancy 5
- Applying TI-RADS results in a meaningful decrease in the number of thyroid nodules biopsied 5