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Emerging Concepts in the Diagnosis and Work-up of Thyroid Cancer

Emerging Concepts in the Diagnosis and Work-up of Thyroid Cancer. APMG Pathologist, MD FCAP. Thyroid Nodules. Found in 4-7% of U.S. adults Approximately 5% are malignant. Fine needle aspiration (FNA) mainstay of diagnosis Bethesda system: Six diagnostic categories

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Emerging Concepts in the Diagnosis and Work-up of Thyroid Cancer

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  1. Emerging Concepts in the Diagnosis and Work-up of Thyroid Cancer APMG Pathologist, MD FCAP

  2. Thyroid Nodules • Found in 4-7% of U.S. adults • Approximately 5% are malignant. • Fine needle aspiration (FNA) mainstay of diagnosis • Bethesda system: • Six diagnostic categories • Correlate with risk of malignancy and recommended clinical management

  3. Bethesda Diagnostic Categories (2009)

  4. Papillary thyroid carcinoma (PTC) • Approximately 85% of thyroid cancers • Often (50-60%) harbor mutations in BRAF gene • Point mutation at codon 600 results in substitution of glutamate for valine (V600E) • Most common mutation in PTC • Mutation found more often in conventional and tall-cell variants

  5. BRAF V600E mutation leads to constitutive activation of the mitogen activated protein kinase (MAPK) signaling pathway

  6. Atypia of Undetermined Significance • 10-15% of fine needle aspirations (FNAs) • 5-15% risk of malignancy • Often referred for diagnostic thyroidectomy • Low but defined risk of complications

  7. BRAF in diagnosis of PTC • BRAF V600E is VERY SPECIFIC (99.8%) for PTC. • BRAF mutation is very strong evidence of PTC • BRAF V600E is NOT SENSITIVE for PTC (49.5%) • Failure to detect a BRAF mutation does NOT rule out PTC. • Niche for BRAF testing in cases with indeterminate cytology? • BRAF testing can increase the ability of FNA biopsy to reach a diagnosis.

  8. Studies evaluating BRAF in thyroid FNAs

  9. BRAF and PTC prognosis • Numerous studies have found that PTC with mutated BRAF have more aggressive features • Extrathyroidal extension, regional metastasis, etc. • Even applies to small lesions (less than 1.0 cm) • However, excellent prognosis in general for PTC • Over 95% 10-year survival rate • Targeted therapy against BRAF unlikely to markedly improve survival

  10. BRAF testing • Predominantly occurs via PCR • Assay should have the ability to detect the mutation in the background of normal cells seen in the cytology • Can be performed on: • Residual cytology sample in preservative solution after cytological examination • Formalin fixed paraffin embedded tissue blocks and slides

  11. Conclusions • BRAF testing can aid in diagnosing papillary thyroid carcinoma from cytology samples • Particularly useful with indeterminate cytology • Identifies PTC with more aggressive features. • May help identify patients needing surgery. • No current role in therapy selection • Full prognostic significance still unknown

  12. Questions? • Contact pathologist with questions or to request testing on a patient: APMG Pathologist, MD FCAP tlpath@domain.com (888) 555-1212

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