Difference between papillary and follicular thyroid carcinoma outcomes: an experience from Egyptian institution

Differentiated thyroid carcinomas (DTCs) are classified into papillary thyroid carcinoma (PTC) and follicular thyroid carcinoma (FTC). DTCs are analyzed as a single group in clinical studies that investigated the prognostic factors and prognosis of these malignancies. However, the biological behaviors of these carcinomas significantly differ. In the present study, we aimed to detect differences in the outcomes between PTC and FTC in Mansoura University Hospital in Egypt.

A total of 558 patients with histologically proven thyroid carcinomas from January 2003 to December 2012 were retrospectively enrolled. The clinical and pathological data of patients were reviewed.

Large primary tumor size, lymph node involvement, extrathyroid extension, and distant metastasis were significant poor prognostic factors for overall survival (OS) in old PTC patients. Cox hazard analysis showed that the patient's age, extra thyroid extension, and distant metastasis were the only independent prognostic factors. In FTC patients, only the distant metastasis and degree of tumor invasion were significant poor prognostic factors in OS univariate analysis. However, these factors were nonsignificant in multivariate analysis. The 10-year OS rates were 97% and 89% for PTC and FTC, respectively (P=0.003). The 10-year disease-free survival (DFS) rates were 77.2% in PTC vs. 65% in FTC (P=0.179).

The significant prognostic factors vary between the two types of DTCs. Therefore, PTC and FTC patients need to be analyzed and reported independently. PTC survival is widely and significantly affected by age, extrathyroid extension, and distant metastasis. By contrast, these factors were nonsignificant in FTC, which showed poorer survival than PTC.