Histopathologic Assessment of Capsular Invasion in Follicular Thyroid Neoplasms-an Observer Variation Study

Area of Science:

• Endocrine Pathology
• Surgical Pathology
• Diagnostic Accuracy

Background:

• Accurate assessment of capsular invasion is critical for diagnosing encapsulated follicular thyroid neoplasms.
• Distinguishing between definite and questionable capsular invasion presents diagnostic challenges.
• Interobserver variability in pathology can affect patient diagnosis and management.

Purpose of the Study:

• To investigate the interobserver agreement among thyroid pathologists in assessing capsular invasion of follicular thyroid tumors.
• To evaluate the impact of invasion assessment variability on final pathological diagnoses, including malignancy.
• To explore diagnostic approaches for cases with questionable capsular invasion.

Main Methods:

• Eleven thyroid pathologists reviewed virtual slides of 20 follicular thyroid neoplasm cases.
• Cases were selected based on differential diagnoses involving definite versus questionable capsular invasion.
• Pathologists categorized invasion as non-invasive, questionable invasive, or clear-cut invasive.

Main Results:

• Fair interobserver agreement was observed for clear-cut invasive (Kappa=0.578) and non-invasive (Kappa=0.404) categories.
• Poor agreement (Kappa=0.186) was found for the questionable invasion category.
• Agreement on final malignancy diagnosis was only fair (Kappa=0.545), highlighting diagnostic discrepancies.

Conclusions:

• Significant interobserver variation exists in evaluating capsular invasion of follicular thyroid neoplasms.
• The assessment of questionable capsular invasion is particularly problematic, leading to diagnostic uncertainty.
• Lack of a uniform approach in questionable cases impacts diagnostic consistency and potentially patient care.