Detection of c-erbB-2 and other tumor markers on bladder tumor specimens: Marked differences after formalin or Bouin's fixation

In the course of a multi-center retrospective study on the prognostic value of bladder tumor markers, it became apparent that tumor samples from one of the Centers showed reactivity patterns outside the normal range of variability. The antibodies investigated were a rabbit antiserum to c-erbB- 2, the monoclonal antibody P12 to LewisX and the monoclonal antibodies (mAb) M344 and 19A211 to bladder tumor-associated antigens. The tumor specimens (total=171) were from comparable patient populations from each Center. The only difference was in the fixation of the tumors, done with formalin in three Centers (12 tumors) and with Bouin's solution (50 tumors) in one Center. Analysis of the results showed significant differences in the rate of positivity between comparable tumors. Positivity of Mab 19A211 with Bouin's tumors was 30% of that with formalin-fixed tumors, while reactivity with the antiserum to c-erbB-2 was four fold more frequent in Bouin's-fixed tumors. The expression of these two antigens is clearly different from that expected from preliminary results and from other published studies. Thus, tissue fixation with Bouin's solution can generate artificially high or low results with some antibodies. This may have important implications in the study of tumor markers by immunohistochemistry.