Oncofetal expression of blood group-related antigen on morules in thyroid carcinoma

Morule formation in association with characteristic biotinrich 'optically clear nuclei' were found in 7 of 2514 cases of thyroid carcinoma. The seven patients were all young females aged from 20 to 36 years who were suffering from either papillary carcinoma (six cases) or follicular carcinoma (one case). The ABH (O) blood group (BG) types were A in three, AB in two and H(O) in two patients. Immunohistochemical study revealed that ABH(O) and Lewis BG antigens were expressed more specifically on morules than on ordinary neoplastic cells of papillary or follicular carcinoma. Lewis BG antigens tested in the present study were as follows: CA50, CA19-9, stage-specific embryonic antigen 1 (SSEA-1), and sialyl SSEA-1. Ulex europaeus agglutinin I (UEA-I) histochemistry showed a positive reaction on all the morules of blood groups A and H(O) patients, but yielded completely negative results on the morules of type AB patients. Sequential digestion by neuraminidase and alpha-galactosidase unmasked the reactivity for UEA-I even on the morules of type AB patients. The consistent reactivity for UEA-I on the morules seemed to be related to specific expression of BG antigens, which were characterized as oncofetal expression. It is suggested that the morules in thyroid carcinoma might be a kind of fetal component induced by the differentiation of the neoplastic cells to the stage of immature embryonic cells.