Clinical Characteristics of Poorly Differentiated Carcinoma of the Thyroid and Comparison of Its Survival to the Tall Cell and Columnar Cell Variants of Papillary Carcinoma

Abstract

Background: Poorly differentiated carcinoma (PDC) of the thyroid includes tall and columnar cell variants (TCV) of the papillary carcinoma as well as the thyroid carcinoma with trabecular, insular and solid (TIS) growth patterns. There have been a few clinical studies on the PDC of the thyroid. We evaluated the clinical characteristics and the outcome of the PDC. Methods: We investigated the clinicopathologic features of the thyroid carcinoma with TIS growth patterns (n = 46) and TCV of the papillary carcinoma (n = 14). We investigated the clinical features of ten patients diagnosed as PDC of the thyroid who had been undergone thyroidectomy for well differentiated carcinoma previously and compared these outcome with those of patients primarily diagnosed as PDC of the thyroid (n = 60). Results: The clinical course of the thyroid carcinoma with TIS growth patterns was slightly more aggressive than that of TCV of the papillary carcinoma. However, disease-specific survivals of both cancers were not significantly different. Disease-specific survival was independently correlated with the presence of distant metastasis at diagnosis and high dose radioiodine therapy. The clinical features and outcome of the patients with PDC detected at recurred sites after operation for well-differentiated carcinoma were more aggressive than those diagnosed as PDC of the thyroid. Conclusion: The prognosis of the thyroid carcinoma with TIS growth patterns and TCV of the papillary carcinoma were similar. The PDC which was detected after thyroidectomy for well-differentiated carcinoma had worse prognosis than primarily diagnosed as PDC of the thyroid.