Underestimated risk of cancer in solitary thyroid nodules ≥3 cm reported as benign

Background: The study aims to assess the risk of cancer in solitary thyroid nodules ≥30 mm in size reported as Bethesda II, and its implications. Method: The clinical records of 202 patients, who underwent thyroid lobectomy for solitary nodules measuring ≥30 mm, reported as Bethesda II on preoperative FNAC between Jan 2015 and Apr 2016 were reviewed. Data collected included nodule size and consistency, and final histopathology results. The risk of cancer and the recommended management according to ATA guidelines were the outcomes of interest. Comparisons were then made between two size categories: (30–40 mm; n = 72; C1) and (>40 mm; n = 130; C2), and two nodule consistencies. Results: Mean nodule size was 43.2 mm (range 30–92). Ninety-five percent were solid and 5% were predominantly cystic. The risk of cancer was 22.8% (46/202) with no size threshold, or graded increase in risk observed. Based on biologic behavior, 50% of cancers were considered clinically significant. Accordingly, the risk of cancer for which surgery is recommended was 11.4% (23/202). The risk of cancer requiring total thyroidectomy was 9.4% and was influenced by nodule size (19 vs. 60% in C1 and C2, respectively; p = 0.01). Predominantly cystic nodules had a greater risk of malignancy compared to predominantly solid nodules even after adjusting for size (40 vs. 9.9%; p = 0.01 and 40 vs. 12.5%; p = 0.02, respectively). Conclusion: The risk of malignancy in Bethesda II solitary nodules ≥30 mm is considerable implying a need for changing the way these are approached and refining cytopathology reporting.