Is increased vascularity of a thyroid mass indicative of malignancy?

From the Guidelines

Increased vascularity of a thyroid mass is not a reliable indicator of malignancy. While some thyroid cancers may show increased blood flow on ultrasound, this finding is actually more commonly associated with benign conditions such as Graves' disease, thyroiditis, and hyperfunctioning nodules. Many malignant thyroid nodules can appear hypovascular or have normal vascularity. When evaluating a thyroid mass, other sonographic features are more predictive of malignancy, including irregular margins, hypoechogenicity, microcalcifications, taller-than-wide shape, and absence of a halo.

Key Points to Consider

• The American Thyroid Association risk stratification system and the Thyroid Imaging Reporting and Data System (TI-RADS) incorporate multiple ultrasound characteristics rather than relying on vascularity alone 1.
• Fine needle aspiration biopsy remains the gold standard for determining if a thyroid nodule is malignant, as imaging features alone cannot definitively diagnose cancer 1.
• The use of various immunohistochemical markers in cytologic samples to differentiate papillary thyroid carcinoma from other follicular-derived lesions of thyroid has been explored, but none of the markers appears to be specific enough to be employed as the diagnostic marker for the cytologic diagnosis of papillary thyroid carcinoma 1.
• Molecular testing for thyroid nodules (BRAF, RAS, RET/PTC and PAX8/PPARγ mutations) has been reported to be a strong indicator of cancer, with ∼97% of mutation-positive nodules having malignant diagnosis at histology 1. Therefore, clinicians should not use increased vascularity as a primary criterion when deciding which thyroid nodules require further investigation.

Recommendations for Practice

• Use a combination of ultrasound characteristics, including irregular margins, hypoechogenicity, microcalcifications, taller-than-wide shape, and absence of a halo, to evaluate the risk of malignancy in a thyroid mass.
• Perform fine needle aspiration biopsy on thyroid nodules with suspicious ultrasound features or clinical suspicion of malignancy.
• Consider molecular testing for thyroid nodules with indeterminate cytology results.
• Use the American Thyroid Association risk stratification system and the Thyroid Imaging Reporting and Data System (TI-RADS) to guide management decisions for patients with thyroid cancer.

From the Research

Vascularity of a Thyroid Mass and Malignancy

• The relationship between the vascularity of a thyroid mass and its potential for malignancy is an area of interest in thyroid cancer diagnosis.
• According to 2, sonographic features of malignancy include microcalcifications, solid mass, absence of halo, and internal blood flow, which can be helpful in predicting thyroid malignancy in a nodule.
• Increased vascularity, indicated by internal blood flow, is one of the sonographic features that may suggest malignancy.

Diagnostic Approaches

• Fine-needle aspiration cytology (FNAC) and high-resolution thyroid ultrasound are currently the most accurate and cost-effective diagnostic approaches for evaluating patients with nodular thyroid disease 3.
• The use of radionuclide thyroid scanning, such as with technetium-99m sestamibi and tetrofosmin, can also be useful in determining recurrent or metastatic differentiated thyroid cancer 2.
• Positron emission tomography (PET) using 18-F-fluorodeoxyglucose has emerged as a useful tool in detecting non-iodine avid dedifferentiated and/or poorly differentiated thyroid cancer 2.

Risk of Malignancy

• A study on the usefulness of standardized uptake value (SUV) in differentiating between benign and malignant thyroid lesions found that a high SUVmax value increases the risk of malignancy 4.
• The risk of malignancy was found to be 16.7% for lesions with a SUVmax under 3,43.8% for lesions with a SUVmax between 3 and 6, and 54.6% for lesions with a SUVmax over 6 4.
• However, it is essential to interpret small lesions with focal uptake of 18F-FDG cautiously, as SUVmax correlated with the diameter of malignant lesions 4.

Treatment and Prognosis

• The treatment options for patients with thyroid cancer include total thyroidectomy, radioactive iodine therapy, and molecular-targeted therapies with tyrosine kinase inhibitors 5.
• Early diagnosis and appropriate treatment can improve prognosis and reduce mortality 5.
• The prognosis and treatment of thyroid cancer depend on the tumor type and its stage at the time of diagnosis, with many thyroid cancers remaining stable, microscopic, and indolent 5.