Immunohistochemical expression of cyclooxygenase 2 in follicular carcinomas of the thyroid

Cyclooxygenase 2 (COX-2) has been shown to be up-regulated and/or overexpressed in a variety of human neoplasms. However, limited data exist on the role of COX-2 in follicular carcinomas of the thyroid. Studies in this area are potentially significant, since therapeutic agents that inhibit COX-2 are currently available and could play a role in treatment.

A retrospective clinicopathologic review with COX-2 immunohistochemical staining of 34 follicular carcinomas and 7 follicular adenomas with incomplete capsular penetration was performed.

The study included 41 patients (25 women; mean age, 50.9 years). All patients underwent gross total resection of the neoplasm. Fifteen carcinoma patients received adjuvant radiotherapy. Seven patients with follicular carcinomas developed recurrent disease: 3 patients were alive (mean follow-up, 10.1 years) and 4 patients died of metastatic disease (mean follow-up, 3.5 years). All remaining patients were disease free (mean follow-up, 5.9 years). Only 1 follicular adenoma with incomplete capsular penetration recurred (patient alive at 9 years). The remaining patients were disease free (mean follow-up, 4.9 years). The COX-2 staining was positive in 11 tumors (9 of 34 follicular carcinomas, 2 of 7 follicular adenomas with incomplete capsular penetration). A greater percentage of recurrences (36% COX-2 positive vs 13% COX-2 negative) and fatal tumors (18% COX-2 positive vs 7% COX-2 negative) occurred in patients who had COX-2-positive staining neoplasms.

Only a few follicular carcinomas (26%) and follicular adenomas with incomplete capsular penetration (29%) express COX-2 by immunohistochemical analysis. The data suggest that such expression of COX-2 may correlate with increased tumor recurrence and death; however, studies with larger numbers of patients will be needed to establish this.