Tumor growth rate of follicular thyroid carcinoma is not different from that of follicular adenoma

Abstract

Objective

Distinguishing malignancy from benign thyroid nodule has always been challenging, especially in follicular lesions. Thyroid nodules with small size and indeterminate cytology do not lead to immediate surgery. We tried to evaluate whether tumor size and tumor growth rate can distinguish follicular thyroid carcinoma (FTC) from follicular adenoma (FA).

Design and Patients

This retrospective study included patients with pathologically proven FTCs (n=50) and FAs (n=110) who underwent preoperative serial neck ultrasonography (US) at least 3 times: it comprises 30% of all follicular tumors (32% FAs and 25% FTCs). The growth rates of follicular tumors on serial US were measured using at least 3 consecutive examinations during a median follow-up of 4.1 years (range, 0.7–13.3 years) by experienced radiologists.

Results

The FA and FTC groups showed no significant difference in clinicopathological characteristics, including age, proportion of large nodules (>4 cm), and preoperative cytology. The maximum diameter of thyroid nodule was gradually increased in both groups with statistical significance (p<0.001, and p<0.001, respectively). No significant differences in change of maximum diameter of thyroid nodule (p=0.132) and tumor volume (p=0.208) were found between the FA and FTC groups during the follow-up. The median time to a significant tumor growth from baseline was not different between the FA and FTC groups (1.4 years, and 1.7 years, respectively, p=0.556). When we divided the patients into four groups (rapid, moderate, slow, and no growth) according to the growth velocity of the thyroid tumors, no significant difference in growth velocity was found among the groups.

Conclusions

The tumor size and growth rate of the thyroid nodule itself could not predict malignancy. Diagnostic approaches that use molecular markers would be more important than clinical features for the decision of diagnostic surgery for patients with follicular tumors.

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