Frozen section analysis in the post-Bethesda era

Area of Science:

• Endocrinology
• Surgical Pathology
• Oncology

Background:

• The utility of frozen section (FS) for indeterminate thyroid nodules remains debated.
• The Bethesda System for Reporting Thyroid Cytopathology (2009) categorizes indeterminate fine-needle aspiration results, including follicular lesions (FL), Bethesda category 3 (BC3), and Bethesda category 4 (BC4).

Purpose of the Study:

• To evaluate and compare the utility of frozen section (FS) in the assessment of Bethesda category 3 (BC3) versus Bethesda category 4 (BC4) thyroid lesions.
• To determine the sensitivity and specificity of FS in differentiating benign from malignant thyroid nodules within these categories.

Main Methods:

• Retrospective review of 479 patients undergoing thyroid lobectomy (January 2008 - July 2014).
• Analysis focused on 135 patients with appropriate Bethesda categorization (65 FL, 45 BC3, 25 BC4).
• Sensitivity and specificity of FS were calculated for each subgroup.

Main Results:

• In the BC4 group, 4 of 25 patients had cancer, with FS correctly identifying 2 (50% sensitivity), leading to FS changing the operation in 8% of cases.
• In the BC3 group, 5 of 45 patients had cancer, with FS identifying only 1 (20% sensitivity), changing the operation in 2.2% of cases.
• For follicular lesions (FL), 6 of 65 patients had cancer, with FS identifying 3 (50% sensitivity), changing the operation in 4.6% of cases.

Conclusions:

• Frozen section (FS) demonstrates improved utility in evaluating Bethesda category 4 (BC4) thyroid nodules compared to BC3.
• The application of FS in BC4 cases may help avoid unnecessary reoperations in 8% of patients.
• The clinical benefit of FS in BC4 is influenced by surgeon practices regarding the management of differentiated thyroid cancer based on size.