Frozen section in a cytological diagnosis of thyroid follicular neoplasm

Fine-needle aspiration biopsy is the most accurate diagnostic test for thyroid nodules, its only limitation being the diagnosis of follicular neoplasm that does not distinguish between benign and malignant follicular lesions.

To determine the utility of intraoperative frozen-section analysis in cases of a cytological diagnosis of follicular neoplasm, a retrospective review of 66 patients with a solitary thyroid nodule and follicular neoplasm who underwent thyroid surgery was carried out.

Fine-needle aspiration was classified following the Papanicolaou Society of Cytopathology Classification, and frozen section was defined as malignant or "deferred." If a malignant diagnosis was made by frozen-section analysis, a total thyroidectomy was carried out. The extension of thyroid surgery in the deferred cases was based on the definitive histological diagnosis.

Sixty-four cases were classified as deferred, and two as suspect for malignancy. Among the 64 deferred cases, 15 were malignant in the final pathological findings, and 49 were benign. The two suspect cases were papillary carcinoma. Frozen-section analysis classified 2 of 17 (11.7%) cases as follicular variant of papillary carcinoma that could not be diagnosed by cytological study. However, these two cases had a strong clinical evidence of malignancy.

The routine use of frozen-section analysis is useless in cases of cytological diagnosis of follicular neoplasm on fine-needle aspiration biopsy, because of the low probability of achieving the diagnosis of follicular carcinoma and the inability to provide additional information apart from the clinical and the cytological data.