What are the characteristic ultrasound features of follicular thyroid cancer?

From the Guidelines

Follicular thyroid cancer is characterized by ultrasound features such as hypoechogenicity, solid aspect, and intranodular blood flow, although these features are not specific and can also be found in benign nodules. When evaluating thyroid nodules, it's essential to consider multiple ultrasound patterns simultaneously, as the presence of several suspicious features can increase the specificity of ultrasound for malignancy, but may decrease sensitivity 1. Some key features to look for in follicular thyroid cancer on ultrasound include:

• Hypoechogenicity (darker than surrounding tissue)
• Solid aspect
• Intranodular blood flow
• Regular margins
• Absence of peripheral halo or presence of a complete or partial hypoechoic halo surrounding the nodule
• Round to oval shape
• Variable size, but nodules larger than 4 cm carry higher suspicion for malignancy It's crucial to note that ultrasound features alone are not sufficient to differentiate between follicular adenoma and carcinoma, and fine needle aspiration (FNA) biopsy followed by histopathological examination is necessary to identify capsular or vascular invasion, which is diagnostic of follicular thyroid cancer 1.

From the Research

Characteristic Ultrasound Features of Follicular Thyroid Cancer

The following are the characteristic ultrasound features of follicular thyroid cancer:

• Hypoechoic lesions 2, 3, 4
• Solid echotexture 3, 4
• Ill-defined or irregular margins 3, 4, 5
• Microcalcifications 3, 4, 5
• Increased vascularity 3, 5
• Taller-than-wide shape 6, 5
• Blurred or microlobulated margins 6
• Interrupted halo and satellite nodule(s) with or without halo ring, which are specific sonographic features for follicular thyroid carcinomas 4
• Cluster of grapes sign, micro-or macro-calcifications, rim calcifications 4

Ultrasound Features Associated with Malignancy

The ultrasound features associated with malignancy in follicular thyroid cancer are:

• Hard lesions to palpation 2
• Solitary nodules 2
• Hypoechoic follicular neoplasms 2
• Size of thyroid nodule more than 30 mm 3
• Fast growth of the nodule 5

Diagnostic Accuracy of Ultrasound Features

The diagnostic accuracy of ultrasound features in distinguishing follicular thyroid cancer from adenoma is:

• High sensitivity and specificity for ill-defined margin, solid echotexture, and microcalcifications 3, 4, 5
• Relatively high sensitivity and specificity for hypoechoic echogenicity and increased vascularity 3