The Bethesda System for Reporting Thyroid Cytopathology (BSRTC) classifies a follicular lesion of undetermined significance as Category III, carrying an estimated malignancy risk in the surgical excision population of approximately what percentage?
- A 1–4%
- B 6–18% ✓
- C 25–40%
- D 50–75%
Correct answer: B. 6–18%
Explanation
Bethesda Category III (atypia of undetermined significance/follicular lesion of undetermined significance, AUS/FLUS) carries an estimated risk of malignancy of 6–18% in the 2023 revised BSRTC, based on surgical follow-up data. Category I (non-diagnostic) is 5–10%; Category IV (follicular neoplasm) is 25–40%; Category V (suspicious for malignancy) is 60–75%. Repeat FNA or molecular testing is the recommended next step for Category III.
Reference: Bailey & Love's Short Practice of Surgery, 27th ed.
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