Thyroid Fine Needle Aspiration Biopsy
(FNAB):
Inside the Eye of a Cytopathologist
Ian Jaffee, MD FCAP
Director of Cytopathology
California Pacific Medical Center
Outline of Discussion
•
•
•
•
Utility of FNAB
Applications to thyroid nodules
Cytology…
Understanding the cytopathology report
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
Good practice in cytopathology
• Direct communication
• Collaboration with endocrinologist, surgeon
(general vs ENT), radiologist, and PCP
• Follow-up correlation with final surgical
pathology
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
Diagnostic approach
• Non-diagnostic
• Benign
• Atypical follicular lesion of undetermined
significance (AFL-US)
• Suspicious for follicular neoplasm/follicular
lesion
• Suspicious for malignancy
• Malignant
Non-diagnostic
• Findings
–
–
–
–
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;59:415-419.
» Renshaw A, Significance of repeatedly non-diagnostic thyroid
FNAs. Am J Clin Pathol 2011;135:750-752
Benign
• “Most things in the thyroid are benign”
• Risk of malignancy (~3%)
Benign Thyroid Nodules (BTN)
• Management: Clinical follow-up
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)
Follicular lesions
•
•
•
•
•
Suspicious for follicular neoplasm
Follicular neoplasm
Follicular lesion
Hürthle cell lesion
Risk of malignancy: ~15-20%
Cytology of follicular lesions
Follicular adenoma
• Capsule; no vascular invasion
Follicular carcinoma
• Capsular invasion
• Vascular invasion
Follicular lesions
• Management Options:
– Lobectomy
– Lobectomy with frozen section
– Total thyroidectomy
– Molecular testing (more later…)
Malignant
• Suspicious for malignancy (risk of malignancy
60-75%)
– Management: Lobectomy vs total thyroidectomy
• Malignant (risk of malignancy 99%)
– Management: Thyroidectomy
Malignant
•
•
•
•
•
•
•
Papillary thyroid carcinoma
Follicular carcinoma
Medullary carcinoma
Anaplastic carcinoma
Poorly differentiated carcinoma
Lymphoma
Metastatic carcinoma
Papillary thyroid carcinoma
PTC: Surgical pathology
Molecular triage of FNA samples
• 60-70% of thyroid malignancies harbor at
least one genetic mutation
– BRAF
– RAS
– RET/PTC
– PAX8-PPARγ
Molecular triage of FNA samples
• Indeterminate by cytology
– AFL-US
– Follicular category
Available tests
• VeraCyte (Afirma)
– 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
Bonus
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)
Tzanck you