Blood group antigen expression in malignant tumors of the thyroid: a parallel between medullary and nonmedullary carcinomas.

Blood group antigen (BGA) expression has been described in many fetal, adult, and tumorous tissues. Synthesis of BGA in the thyroid gland is regarded as oncofetal due to blood group structures that are detected in fetal and carcinomatous tissues but not in the normal adult organ. This study examined the prevalence of type 1 (CA-50, CA-19-9, Lea, Leb, A, B, H type 1) and type 2 (Le(x), Le(y), A, B, H type 2) antigens in normal thyroid (n = 25), papillary (n = 104), follicular (n = 52), anaplastic (n = 33), and medullary (n = 48) carcinomas of the thyroid. While normal thyroid tissue expressed no BGA, there was a significant increase of BGA expression in carcinomas of the thyroid gland. There are two theories about the possible origin of C cells, from which the medullary carcinomas arise. Some authors postulate that C cells belong to the amine precursor uptake and decarboxylation system and therefore derive from the neural crest, while others believe that C cells originate from the fifth pharyngeal pouch, as do the follicular cells. The results obtained in this study show that medullary and nonmedullary carcinomas correspond to one another in their BGA expression profile. Therefore it is concluded that medullary carcinomas may have the same origin as nonmedullary tumors of the thyroid.