Sonographic differences between conventional and follicular variant papillary thyroid carcinoma

Area of Science:

• Endocrinology
• Radiology
• Oncology

Background:

• Follicular variant papillary thyroid carcinoma (FVPTC) presents diagnostic challenges due to less aggressive cytologic findings compared to conventional papillary thyroid carcinoma (CPTC).
• Current guidelines emphasize sonographic features for guiding thyroid nodule biopsy decisions.
• Distinguishing FVPTC from CPTC using ultrasound is crucial for appropriate patient management.

Purpose of the Study:

• To compare the sonographic features of conventional papillary thyroid carcinoma (CPTC) and follicular variant papillary thyroid carcinoma (FVPTC).
• To assess the utility of the British Thyroid Association (BTA) U-classification system in differentiating these thyroid cancer subtypes.

Main Methods:

• Retrospective analysis of preoperative ultrasound data from 79 patients (48 CPTC, 31 FVPTC) at an academic teaching hospital.
• A radiologist, blinded to histology, classified nodules using the BTA U-classification system (U1-U5).
• FVPTC subtypes (encapsulated, partly encapsulated, infiltrative) were determined by pathological review.

Main Results:

• FVPTC demonstrated significantly fewer calcifications, microcalcifications, and irregular/lobulated margins compared to CPTC.
• FVPTC nodules were less frequently classified as suspicious (U4) or malignant (U5) on ultrasound (p < 0.01).
• Infiltrative FVPTC subtypes were more likely to exhibit suspicious/malignant sonographic features than non-infiltrative subtypes.

Conclusions:

• Follicular variant papillary thyroid carcinoma (FVPTC) typically exhibits less concerning sonographic features than conventional papillary thyroid carcinoma (CPTC).
• Sole reliance on ultrasound findings may be insufficient to rule out FVPTC.
• Sonographic evaluation should be interpreted cautiously, considering the potential for FVPTC to present with benign-appearing features.