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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.
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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%
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
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
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) Final comments