The Bethesda System for Reporting Thyroid Cytopathology classifies FNA results into 6 categories. A Bethesda III (Atypia of Undetermined Significance/Follicular Lesion of Undetermined Significance — AUS/FLUS) carries an approximate risk of malignancy of:
- A 6–18% ✓
- B 1–4%
- C 25–40%
- D 60–75%
Correct answer: A. 6–18%
Explanation
Bethesda 2023 revised malignancy risks: Category I (non-diagnostic) — 5–10%; II (benign) — 0–3%; III (AUS/FLUS) — 6–18%; IV (follicular neoplasm) — 10–40%; V (suspicious for malignancy) — 45–75%; VI (malignant) — 97–99%. For Bethesda III, repeat FNA, molecular testing (ThyroSeq/Afirma), or diagnostic lobectomy are management options depending on clinical and sonographic risk factors. Repeat FNA is typically performed after 3 months.
Reference: Bailey & Love's Short Practice of Surgery, 27th ed.
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