Bethesda System for Reporting Thyroid Cytopathology

Bethesda System for Reporting
Thyroid Cytopathology
Standardized cytologic diagnosis for thyroid FNA
Dr. Vinesia Lestari Riddi, SpPA, MPH
RS Kanker Dharmais-Pusat Kanker Nasional

Introduction
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Bethesda System for Reporting Thyroid Cytopathology
Fine-needle aspiration (FNA) is among the first diagnostic tools used in the evaluation of thyroid nodules
Thyroid FNA offers high positive predictive value (97%–99%), with sensitivities 65% to 99% and specificities of 72% to 100%
Many potential diagnostic pitfalls exist that can lead to false-positive (0-28%) and/or false-negative (1-35%)

Bethesda System for Reporting Thyroid Cytopathology
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Bethesda System for Reporting Thyroid Cytopathology
BSRTC is the internationally accepted classification to communicate cytological diagnosis in a uniform and unambiguous way

Risk of Malignancy and Management
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Bethesda System for Reporting Thyroid Cytopathology

Criteria for Adequacy
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Bethesda System for Reporting Thyroid Cytopathology
A thyroid FNA sample is considered adequate for evaluation if it contains a minimum of six groups of well-visualized (i.e., well stained, well preserved, undistorted, and unobstructed) follicular epithelial cells with at least ten cells per group.
These six groups of ten follicular cells could be either on one slide or distributed among several for adequacy determination.
These criteria apply to all cytologic preparations (including conventional smears and liquid-based samples).

Exceptions to Adequacy Criteria
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Bethesda System for Reporting Thyroid Cytopathology
Exceptions to this requirement apply to a limited number of case types, including:
Aspirates with cytologic atypia
Solid nodules with inflammation
Colloid nodules

1. Non-diagnostic / Unsatisfactory
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Bethesda System for Reporting Thyroid Cytopathology
Incidence : 10%
Do not meet the criteria for adequacy
Recommendation : FNA with USG guidance

Pitfalls: Cystic Papillary Thyroid Carcinoma
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Bethesda System for Reporting Thyroid Cytopathology
• Rule out papillary thyroid carcinoma, cystic variant
• Up to 10–16 % of PTC can be cystic
• In cystic change, malignant tumor cells commonly misinterpreted as macrophages (non diagnostic) → false negative

Importance of USG-guided FNA
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Bethesda System for Reporting Thyroid Cytopathology

USG-guided FNA Technique
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Bethesda System for Reporting Thyroid Cytopathology

2. Benign
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Bethesda System for Reporting Thyroid Cytopathology
Adequate for evaluation and consists of colloid and benign-appearing follicular cells in varying proportions 
Included entities: 
Benign follicular nodule: 
Colloid nodules 
Nodular goiter 
Hyperplastic (adenomatoid) nodules 
Nodules in Graves’ disease 
Thyroiditis
Lymphocytic thyroiditis 
Granulomatous thyroiditis

Benign Cytology: Colloid & Follicular Cells
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Bethesda System for Reporting Thyroid Cytopathology

Benign Cytomorphologic Features
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Bethesda System for Reporting Thyroid Cytopathology
• Monolayered sheets of follicular cells
• Occasional three dimensional balls/spheres
• Evenly spaced nuclear arrangement
• Follicular cell nuclei are round to oval, approximately the size of a red blood cell
• Colloid background

Benign Cytology: Microscopy
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Bethesda System for Reporting Thyroid Cytopathology

3. Atypia of Undetermined Significance (AUS)
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Bethesda System for Reporting Thyroid Cytopathology
Specimens that contain cells (follicular, lymphoid, or other) with architectural and/or nuclear atypia that is not sufficient to be classified as suspicious for a follicular neoplasm, suspicious for malignancy, or malignant; but more marked than can be ascribed confidently to benign changes.

4. Follicular Neoplasm
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Bethesda System for Reporting Thyroid Cytopathology
• ROM 25-40%
• Significant architectural atypia
• Predominant microfollicles and trabeculae
• Cellular smear
• Mild nuclear change may be seen (no INCIs or papillae)
• Colloid scant or absent
• Lobectomy is necessary for definitive diagnosis

Follicular Neoplasm: Cytology
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Bethesda System for Reporting Thyroid Cytopathology

Follicular Neoplasm: Cellular Smears
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Bethesda System for Reporting Thyroid Cytopathology

Follicular Neoplasm, Hürthle Cell Type
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Bethesda System for Reporting Thyroid Cytopathology

Hürthle Cell Type: Cytology
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Bethesda System for Reporting Thyroid Cytopathology

5. Suspicious for Malignancy
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Bethesda System for Reporting Thyroid Cytopathology
ROM: 65-75% 
Cytomorphologic features (most often those of PTC) raise a strong suspicion of malignancy but the findings are not sufficient for a conclusive diagnosis 
Included entities: 
Suspicious for papillary carcinoma (FVPTC/NIFTP may include in this category) 
Suspicious for medullary carcinoma 
Suspicious for lymphoma 
Suspicious for metastatic

Suspicious for Malignancy: Cytology
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Bethesda System for Reporting Thyroid Cytopathology

6. Malignant
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Bethesda System for Reporting Thyroid Cytopathology
Includes :
• Papillary carcinoma
• Medullary carcinoma
• Lymphoma
• Metastatic tumors

Malignant Cytology: Papillary Carcinoma
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Bethesda System for Reporting Thyroid Cytopathology

Papillary Thyroid Carcinoma
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Bethesda System for Reporting Thyroid Cytopathology

Medullary Thyroid Carcinoma
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Bethesda System for Reporting Thyroid Cytopathology

Other Tumors
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Bethesda System for Reporting Thyroid Cytopathology
Lymphoma
Metastatic Adenocarcinoma

Notes
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Bethesda System for Reporting Thyroid Cytopathology
FNAB cannot diagnose follicular carcinoma because in follicular carcinoma it requires demonstration of capsular invasion or vascular invasion which cannot be seen in FNAB.
NIFTP cannot be definitively diagnosed by FNA; its diagnosis requires histologic examination of the resected lesion.
Bethesda category SHOULD NOT become the sole determinant of management.
Clinical relevances + ultrasound + Bethesda category = management

Terima Kasih
Source :
• Ali SZ, Baloch ZW, Cochand-Priollet B, et al. The 2023 Bethesda System for Reporting Thyroid Cytopathology. Thyroid. 2023.