Thyroid follicular neoplasm: analysis by fine needle aspiration cytology, frozen section, and histopathology.

We performed a retrospective analysis of follicular neoplasm data obtained from frozen section examinations of thyroid nodules. A total of 5,660 patients underwent preoperative neck ultrasonography and fine-needle aspiration cytology (FNAC), surgical treatment, and follow-up at a medical institute. Patients with papillary thyroid microcarcinoma were excluded from this study. In 971 cases, frozen section examination was performed during the surgical treatment of follicular neoplasm that was diagnosed via FNAC. Thyroid malignancies were histologically confirmed in 25.1% of cases (244/971). Among the patients with papillary thyroid carcinoma, 45 were diagnosed with the follicular variant of papillary thyroid carcinomas (27.4%). The diagnostic sensitivity of frozen section for the nonfollicular variant of papillary thyroid carcinoma was better than that for the follicular variant of papillary thyroid carcinoma (89.1% versus 78.9%; P = 0.1023). For 12 cases the diagnosis was atypical follicular adenomas. The diagnostic accuracy of frozen section in cases of follicular neoplasm was 76.9% with a sensitivity of 84.8% and a specificity of 98.9%. In conclusion, our analysis revealed high rates of accuracy when using frozen tissue sections for early diagnosis and treatment of follicular neoplasm; thus, an early decision to extent of surgery prevents a risky follow-up surgery.