USE OF IMMUNOSTAINS TO ABH BLOOD CROUP ANTIGENS TO RESOLVE PROBLEMS IN IDENTITY OF TISSUE SPECIMENS

Identification of contaminating tissue fragments as ''floaters'' is a common problem in surgical pathology. They may be introduced at severa l steps in the processing of specimens, and they are capable of causin g interpretative consternation. Using immunohistochemistry with monocl onal antibodies to blood group isoantigens A, B, and H, we studied nin e cases in which floaters were present. In five of the study cases, di scordant blood group immunostains allowed identification of the artifa ctual tissue fragments. By chance, the other four specimens contained probable floaters from patients whose blood groups were concordant wit h those from whom the ''native'' tissue had been obtained. These resul ts indicate that in some instances, blood group immunostains may resol ve interpretative difficulties surrounding floaters. It is likely that application of immunostains, directed at additional blood group antig ens, will extend the utility of this procedure.