Thyroid nodules are most often discovered during routine physical or instrumental examinations.
What should be the clinician's next steps once a thyroid nodule is confirmed?
The first priority is Differentiating benign nodules from nodules suspicious for malignancy.
Both the first and subsequent visits should answer three main questions:
- Are there symptoms of compression such as dysphagia, dysphonia, or dyspnea?
- Does a nodule change thyroid function? The examination of the node begins with the determination of TSH.
- Is the clinical appearance of a nodule indicative of malignancy? Although the vast majority of thyroid nodules are benign, 5-10% are found to be malignant.
Ultrasonography of the thyroid gland and surrounding neck structures is an important tool in differentiating a benign nodule from one at high risk of malignancy. The American Thyroid Association (ATA) and American College of Radiology Thyroid Image Reporting and Data System (ACR TI-RADS) guidelines are a good guide in this process.
Based on the ultrasound image, the ATA guideline groups thyroid nodules as: Benign, very low risk, low risk, moderate risk, and high risk nodes.
Benign nodules This category includes completely cystic nodules without a tissue component. The risk of malignancy of such nodules is less than 1% and their monitoring can be continued without biopsy. If appropriate, drainage of large symptomatic cysts can be performed.
Very low risk nodes This category includes nodules with a clouded structure (>50% of the nodule consists of microcystic spaces) and partially cystic nodules that do not exhibit high-risk features (Figures 1, 2). The risk of malignancy for such nodules is less than 3% and can be monitored without biopsy. However, if the nodule is larger than 2 cm, biopsy may be warranted.
little In the risk category Isoechogenic and hypoechogenic nodules of tissue structure, as well as partially cystic nodules with tissue arch, are encountered, even without high-risk features (Figure 3). The risk of malignancy of such nodules is 5-10%, and the ATA recommends that a biopsy be performed when the size is greater than 1,5 cm.
In the moderate risk category Hypoechoic tissue nodules without high-risk features are considered (Figure 4). In this case, the risk of malignancy is 10-20% and biopsy should be performed if the size is more than 1 cm.
High-risk nodes The category includes nodules of solid or partially cystic composition that have the following characteristics: High-risk features: irregular contours, microcalcifications, taller than wide shape, peripheral annular calcification with small extrusions, or evidence of extraglandular extension (Figures 5,6). At this time, the risk of malignancy is 70-90% and biopsy should be performed in cases of 1 cm in size. Sonographically suspicious cervical lymph nodes fall into the same category (Figures 7,8). This emphasizes the need to also examine the anterior cervical lymph nodes during every thyroid examination.
Thyroid cytopathology
The Bethesda system groups thyroid cytopathology as follows:
- Undiagnosable
- Benign: The risk of malignancy in the diagnosis of a benign nodule is 0-3%. Its monitoring can be continued with ultrasonography. If the development of high-risk ultrasound signs is observed in the dynamics, a repeat biopsy should be performed.
- Atypia of undetermined significance/follicular lesion of undetermined significance
- Follicular neoplasmA: This category, along with atypia and follicular lesions, includes nodules of unknown nature, which have a 10-40% risk of malignancy. The next step in diagnosis is either molecular marker testing or diagnostic lobectomy.
- Suspected of malignancy: The risk of malignancy in this category is 45-60%. The recommendation is surgical intervention: lobectomy or total thyroidectomy.
- Malignant: This finding is 95-99% likely to indicate the presence of a malignant nodule. The recommendation here is also surgical intervention with lobectomy or total thyroidectomy.
The ACR TI-RADS guidelines use essentially the same system of risk assessment for malignancy as the ATA. In this guideline, the decision to biopsy a nodule or to continue surveillance without biopsy is based on the sonographic features and size of the nodule, as well as informed patient choice, the presence of other comorbidities, and age.
Both the performance of the ultrasound itself and the use of the risk assessment system are highly individual and depend on the physician who evaluates the patient. Since there is no strict agreement on the method of assigning nodules to categories, the physician's personal experience and opinion are of great importance. To avoid unnecessary biopsies and improve the outcome, it is important that the studies are performed in a specialized clinic by physicians with experience in thyroid studies.
Source: medscape.com
