1. Thyroid Fine Needle Aspiration Biopsy (FNAB): Inside the Eye of a Cytopathologist
Ian Jaffee, MD FCAP
Director of Cytopathology
California Pacific Medical Center

2. Outline of Discussion Utility of FNAB Applications to thyroid nodules
Cytology…
Understanding the cytopathology report

3. FNA of the Thyroid Gland
Safe, widely accepted, and cost-effective
Accurate “triage” of the thyroid nodule
Current estimates of ~30,000,000 people in U.S. with thyroid nodules > 1 cm
~30,000 with malignant thyroid nodules
Goal: Identify patients who require surgical intervention

4. Good practice in cytopathology
Direct communication
Collaboration with endocrinologist, surgeon (general vs ENT), radiologist, and PCP
Follow-up correlation with final surgical pathology

5. Good practice in cytopathology
Benign
Malignant
The in betweens…
Suboptimal samples (quality/quantity)
Diagnostic guidelines
Papanicolaou Society of Cytopathology Task Force
American Thyroid Association
None have been necessarily universally accepted

6. Diagnostic approach Non-diagnostic Benign
Atypical follicular lesion of undetermined significance (AFL-US)
Suspicious for follicular neoplasm/follicular lesion
Suspicious for malignancy
Malignant

7. Non-diagnostic Findings Management: Follow-up U/S and repeat FNA
Blood only
Absence of colloid
Insufficient cellularity (“6/10 rule”)
Colloid only (cyst contents)
Management: Follow-up U/S and repeat FNA
Repeated non-diagnostics and risk of malignancy
“quite low” (<5%)
McHenry CR, Walfish PG, Rosen IB. Non-diagnostic fine-needle aspiration biopsy: a dilemma in management of nodular thyroid disease. Am Surg. 1993;59:
Renshaw A, Significance of repeatedly non-diagnostic thyroid FNAs. Am J Clin Pathol 2011;135:

8. Benign “Most things in the thyroid are benign”
Risk of malignancy (~3%)

11. Benign Thyroid Nodules (BTN)
Management: Clinical follow-up

12. Atypical follicular lesion of undetermined significance (AFL-US)
I don’t use it
Poorly defined category
Theoretical risk of malignancy is 5-15%
Management: Repeat FNA or molecular triage (more later)

13. Follicular lesions Suspicious for follicular neoplasm
Hürthle cell lesion
Risk of malignancy: ~15-20%

14. Cytology of follicular lesions

16. Follicular adenoma
Capsule; no vascular invasion

18. Follicular carcinoma
Capsular invasion
Vascular invasion

20. Follicular lesions Management Options: Lobectomy
Lobectomy with frozen section
Total thyroidectomy
Molecular testing (more later…)

21. Malignant Suspicious for malignancy (risk of malignancy 60-75%)
Management: Lobectomy vs total thyroidectomy
Malignant (risk of malignancy 99%)
Management: Thyroidectomy

22. Malignant Papillary thyroid carcinoma Follicular carcinoma
Medullary carcinoma
Anaplastic carcinoma
Poorly differentiated carcinoma
Lymphoma
Metastatic carcinoma

23. Papillary thyroid carcinoma

27. PTC: Surgical pathology

29. Molecular triage of FNA samples
60-70% of thyroid malignancies harbor at least one genetic mutation
BRAF
RAS
RET/PTC
PAX8-PPARγ

30. Molecular triage of FNA samples
Indeterminate by cytology
AFL-US
Follicular category

31. Available tests VeraCyte (Afirma) Asuragen Quest
mRNA gene expression classifier
High NPV (>90%) but modest specificity (50+%)
Asuragen
Reportedly specific (rule-in/confirmatory)
RNA-based assay (RAS, BRAF, RET/PTC, and PAX8-PPARγ)
Quest

33. Bonus

35. Final comments
FNAB is highly accurate with high sensitivity and specificity
Accuracy in diagnosing thyroid abnormalities
dependant on the expertise of the cytopathologist interpreting the biopsy specimen
physician performing the biopsy
Categorization of samples
Non-diagnostic
Benign
AFL-US
Follicular (Suspicious for) lesion/neoplasm
Suspicious for malignancy
Malignant
FNA cannot reliably distinguish benign from malignant follicular neoplasm
New molecular triage testing (lukewarm)

36. Tzanck you