Prognostic factors in follicular carcinoma of the thyroid: a study of 198 cases

Prognostic parameters for papillary carcinoma of the thyroid have been defined by several groups. However, no such study has been reported for follicular carcinoma.

We undertook a retrospective study of well-differentiated carcinoma of the thyroid operated at the Tata Memorial Hospital during the period 1970-1985. In our series, follicular carcinoma formed 48% of the well-differentiated carcinomas of the thyroid. The variables age, sex, size, extrathyroidal spread, distant metastases, and lymph node metastases were evaluated. The survival was plotted according to the Kaplan-Meier method, and graphs compared by log-rank test. Univariate and multivariate analyses were performed.

Based on our experience we stratified the cases into low-risk and high-risk groups. The low-risk group included: age below 40 years, tumor size less than 5 cm. and no extrathyroidal extension or metastases. This low risk group had 100% survival at 15 years, compared with 40% survival for the high-risk group (P <.001). Seventy-three percent (73%) of our cases were in the high-risk group.

Based on our findings that the majority of our patients were in the high-risk group, we advocate a total or near-total thyroidectomy in treatment of follicular carcinoma of the thyroid. There is a need to arrive at a universally acceptable classification of risk groups in follicular carcinoma of the thyroid gland.