Comparison of histology and immunohistochemistry with thyroglobulin serum levels and radioiodine uptake in recurrences and metastases of differentiated thyroid carcinomas

Abstract

The importance of lightmicroscopical and immunohistochemical features of 38 recurrent differentiated thyroid carcinomas (27 papillary carcinomas (PC), 11 follicular carcinomas (FC)) for post-operative serum thyroglobulin (TG) concentrations was analyzed with regard to pre-operative serum TG levels with tumor type, histological and cytological differentiation, volume fraction of TG synthesizing tumor cells (TG immunohistomorphometry), tumor volume and radioiodine uptake (RIU). Serum TG concentration increased with tumor size and the number of TG synthesizing tumor cells (r = 0.5). PC and FC did not differ in their volume proportions of TG synthesizing tumor cells, while TG serum levels in FC significantly exceeded those of PC of similar size. The low TG serum levels found in PC might be explained by a specific defect in thyroglobulin secretion. Carcinomas with partial or total cytologic metaplasia (e.g., oxyphilic carcinomas) had low volume proportions of TG synthesizing cells and low serum TG levels. Thirteen of the 38 differentiated carcinomas (34.2%) showed both high TG serum levels and positive RIU, 17 (44.7%) disclosed only elevated TG serum levels and 6 (15.8%) a positive RIU. In 2 cases (5.3%) TG serum levels were not elevated and RIU''s were negative. TG immunostaining was positive in all 38 cases. TG serum levels depend on the following morphologic factors in differentiated thyroid carcinomas: number of TG synthesizing tumor cells, mode of TG secretion and cytological differentiation of the tumor cells. Serum TG levels did not predict total body I scan.