Follicular variant of papillary thyroid carcinoma. A clinicopathologic study.

BACKGROUND

A retrospective clinicopathologic study was performed to identify the influence of diagnostic and therapeutic procedures on the outcomes of patients with the follicular variant of papillary thyroid carcinoma (FVPTC).

METHODS

The results of 37 patients with FVPTC were compared with those of 37 randomly selected patients with papillary carcinoma and 22 patients with follicular carcinoma. Diagnostic, therapeutic, and follow-up data were obtained by review of clinical and histologic materials.

RESULTS

Median follow-up was approximately 3 years in all groups. Fine-needle aspiration had a sensitivity of 75% for FVPTC, which was similar to that for papillary carcinoma. Frozen section evaluation had a sensitivity of only 27% for FVPTC but 94% for papillary carcinoma and 44% for follicular carcinoma. All patients for whom the fine-needle aspiration specimen contained cytologic features of papillary carcinoma and frozen section suggested a follicular lesion proved to have FVPTC: Consequently, hemithyroidectomy was performed three times more often among patients with FVPTC than among those with papillary carcinoma. FVPTC tumors were modestly, but significantly, smaller than papillary carcinoma tumors (1.2 versus 1.6 cm). Metastases to cervical lymph nodes occurred least often in patients with FVPTC and usually were detected within 3 months of diagnosis. The frequency of distant metastases within this limited period of follow-up did not differ between FVPTC and papillary carcinoma.

CONCLUSIONS

Fine-needle aspiration appears to be superior to frozen section for identification of FVPTC, although the number of aspirations performed was limited. Greater use of aspiration may permit more appropriate surgical management of this disease. Local and distant metastases of FVPTC do not occur more often than do those of papillary carcinoma.