Purpose: Fine needle aspiration cytology (FNA) and frozen section (FS) have been extremely valuable tools in the evaluation of thyroid nodules. However, in follicular carcinomas, it is often difficult to distinguish between a benign and a
malignant
lesion. The aims of this study were to evaluate the characteristic clinicopathologic findings and sensitivities of FNA and FS examination in the diagnosis of follicular carcinomas and to delineate the influence of preoperative and intraoperative
clinicopathologic findings and the prognostic factors on the extent of surgery. Methods: The cases of 33 patients who had undergone thyroid surgery and who had been histologically diagnosed as having follicular thyroid carcinomas were reviewed
for
age,
sex, laboratory findings, FNA findings, frozen-section results, extent of surgery, completion thyroidectomy, and coexistent pathology. Results: There were 28 women and 10 men (2.3：1 ratio) whose ages ranged from 14 to 75 years with a mean of
40.8
years. The mean follow-up was 27.2 months. The most prominent sign was an asymptomatic palpable anterior neck mass, which was present in 29 (87.8%) cases. Fine needle aspiration cytology was performed in 31 patients, revealing a follicular
neoplasm
in
16 patients (sensitivity=51.6%), an adenomatous goiter in 6 (19.4%), a papillary carcinoma in 5 (16.1%), and an anaplastic carcinoma in 1 (3.2%); the specimens were inadequate in 3 patients (9.7%). Among the 32 patients having an intraoperative
frozen
sections, only 7 patients (sensitivity=21.2%) were correctly diagnosed as having cancer. The diagnoses were deferred (reported as a follicular neoplasm) in 21 patients (65.6%) and were changed from benign at frozen section to malignant on final
diagnosis in 4 patients (12.6%). Among the 21 patients diagnosed as having a follicular neoplasm on frozen section, 10 patients (47.6%) were treated with a subtotal thyroidectomy, 6 patients (28.6%) with a total thyroidectomy taking into
consideration
the gross findings at operation and prognostic factors such as AGES and AMES to reduce the incidence of a completion thyroidectomy. Only 5 patients (23.8%) underwent a lobectomy followed by a reoperation (a completion thyroidectomy). Conclusion:
Fine
needle aspiration cytology and frozen section results are not good indicators in making the decision regarding the extent of the thyroidectomy. A definitive decision to avoid a completion thyroidectomy should be made during the initial operation
based
on gross findings, frozen-section results, and prognostic factor such as age, tumor grade, tumor size, and the presence of extracapsular spread or distant metastasis.
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