Papillary Thyroid Carcinoma Overexpresses Fully and Underglycosylated Mucins Together with Native and Sialylated Simple Mucin Antigens and Histo-Blood Group Antigens.

We studied the immunohistochemical expression of mucins (MUC1, underglycosylated MUC1, MUC2, MUC5AC, and MUC6), simple mucin antigens (Tn, sialyl Tn, and T), and histo-blood group antigens (type 1-Lewis(a) and sialyl Lewis(a) type 2-Lewis(x) and sialyl Lewis(x)) in a series of 26 papillary thyroid carcinomas (PTC), 6 follicular carcinomas, and a control group of 32 cases of "normal" thyroid parenchyma adjacent to the tumors. PTC expressed more often, more intensively, and more extensively every antigen but MUC6, which was not observed in any case. The expression of MUC5AC was also extremely rare. MUC1 expression was related to the expression of underglycosylated MUC1, MUC2, Lewis(a), and sialyl Lewis(a). A trend toward an association between the expression of MUC1 and that of type 2 histo-blood group antigens was also observed. Whenever there was a dissociation between the expression of type 1 and type 2 Lewis antigens, MUC1 appeared closely related to type 1 and independent from type 2 histo-blood group antigens. We conclude that MUC1 plays a pivotal, though not exclusive, role in the glycosylation features of well differentiated thyroid carcinomas. Despite the prominent expression of mucins and carbohydrate antigens in PTC, no significant differences were observed between PTC and follicular carcinoma thus ruling out the possibility of using the aforementioned antigens as diagnostic markers per se.