Prognostic factors of insular versus papillary/follicular thyroid carcinoma

The study aims were to characterize patients with insular thyroid cancer and to provide data on patient outcome after surgical therapy. We compared nine patients with insular thyroid cancer at the Department of Surgical Science of "La Sapienza" University of Rome with 27 patients of similar age and tumor size who had follicular and papillary cancer, for a minimum follow-up period of 24 months (range, 24-72 months). All of the patients examined underwent total thyroidectomy. Vascular invasion was observed in 44.4 per cent of insular carcinomas (P < 0.05 vs papillary carcinomas). No significant differences were observed regarding diagnostic method, multifocality, tumor nodes metastases (TNM), or stage. The death rate of patients with insular carcinoma (33.3%) was found to be higher than that of patients with follicular carcinoma (P < 0.05) and papillary carcinoma (P < 0.01). Relapsing lymph-node pathologies were observed in 4 patients (44.4%) with insular carcinoma (P < 0.05 vs those with follicular and papillary carcinomas). Distant metastases were observed in 66.6 per cent of insular carcinomas (P < 0.005 vs follicular carcinoma and P < 0.001 vs papillary carcinoma). At the end of follow-up, 2 patients (22.2%) with insular carcinoma were disease-free (P < 0.001 vs those with follicular and papillary carcinomas). Our study demonstrates an unfavorable prognostic role of the insular phenotype of thyroid cancer, such that this tumor can be classified as an autonomous clinical and pathological entity.