Thyroid blood group isoantigen expression: a parallel with ABH isoantigen expression in the distal colon.

An interesting and not previously reported parallel has been observed between the known pattern of ABO (H) blood group isoantigen expression in normal and neoplastic colonic epithelium and that in the thyroid. Epithelial expression of blood group isoantigens was not observed in 16 specimens of normal or non-neoplastic thyroid tissue. This contrasts with the progressive re-expression of these antigens in neoplastic thyroid tissue. Blood group isoantigens were detected in two of eight papillary adenomas and 13 of 17 papillary carcinomas. Antigen expression was in part related to differentiation, and stained cells were less readily detected in follicular tumours, only one of five adenomas and two of seven carcinomas displaying blood group antigens while three medullary and two anaplastic carcinomas were antigen-deficient.