Risk stratification in follicular neoplasm: a cytological assessment using the modified Bethesda classification

Area of Science:

• Endocrinology
• Cytopathology
• Surgical Pathology

Background:

• The 2007 Bethesda classification for thyroid cytology defines follicular neoplasm with limited diagnostic specificity.
• Current management for follicular neoplasm often involves diagnostic lobectomy, with challenges in accurate triaging.
• The study institution subclassified follicular neoplasm into microfollicular-patterned neoplasm (MN), Hürthle cell neoplasm (HN), and follicular lesion (FL) for improved accuracy.

Purpose of the Study:

• To evaluate the diagnostic accuracy and follow-up trends of a modified follicular neoplasm classification system.
• To assess the malignancy risk associated with subcategories of follicular neoplasms.
• To identify specific cytological features predictive of malignancy in follicular lesions.

Main Methods:

• A retrospective review of 399 thyroid fine-needle aspiration cases diagnosed as follicular neoplasm between January 2008 and December 2012.
• Correlation of cytological diagnoses with subsequent surgical pathology reports.
• Analysis of cytological features, including nuclear enlargement and nuclear grooves, for association with malignancy.

Main Results:

• Malignancy was identified in 32% of all follicular neoplasms.
• The follicular lesion (FL) category showed a significantly higher malignancy rate (73%) compared to microfollicular-patterned neoplasm (MN) (29%) and Hürthle cell neoplasm (HN) (26%).
• Nuclear enlargement and nuclear grooves were significantly associated with the follicular variant of papillary thyroid carcinoma.

Conclusions:

• Follicular lesions with subtle nuclear atypia have a high positive predictive value for malignancy and warrant distinct management.
• The findings suggest a need to refine current thyroid fine-needle aspiration classification systems, potentially by subclassifying follicular neoplasms.
• Risk stratification based on subclassification of follicular neoplasms is crucial for appropriate surgical management.