A simplified four-tier classification for thyroid core needle biopsy.

Area of Science:

• Endocrinology
• Pathology
• Oncology

Background:

• Core-needle biopsy (CNB) is a key diagnostic tool for thyroid nodules.
• A standardized histological classification for CNB specimens is lacking, hindering consistent interpretation.
• Existing systems, like the Bethesda System for Fine Needle Aspiration Cytology (FNAC), highlight the need for similar standardization in CNB.

Purpose of the Study:

• To propose a simplified histological classification for thyroid nodule CNB specimens.
• To establish four distinct diagnostic categories (DC) with defined risks of malignancy (ROM) and expected incidences.
• To address the lack of a uniform scheme for CNB categorization in thyroid nodule diagnosis.

Main Methods:

• Retrospective analysis of 6284 CNBs from a single institution where CNB is routinely used.
• Classification of biopsies into non-diagnostic, benign, follicular tumour (FT), and malignant categories.
• Correlation of CNB findings with surgical pathology for nodules that underwent surgery post-biopsy.

Main Results:

• Out of 6284 CNBs, 9.7% were malignant and 6.9% were classified as follicular tumours (FT).
• For nodules undergoing surgery, the risk of malignancy (ROM) was 2.2% for benign, 12.4% for FT, and 98.3% for malignant CNBs.
• The classification achieved high sensitivity (94.7%) and positive predictive value (65.6%) for malignancy when combining FT and malignant categories.

Conclusions:

• The proposed histological classification for thyroid nodule CNB demonstrates high diagnostic accuracy.
• The system effectively minimizes indeterminate categories, improving diagnostic clarity.
• Application in Western practice revealed a low ROM for FT, suggesting potential benefit from immunohistochemical studies for refinement.