IMMUNOHISTOCHEMICAL DEMONSTRATION OF C-ERBB-2 ONCOPROTEIN IN GASTRIC ADENOCARCINOMA - COMPARISON OF CRYOSTAT AND PARAFFIN WAX SECTIONS AND EFFECT OF FIXATION

Aims-To investigate the effects of fixation on the immunohistochemical demonstration of c-erbB-2 oncoprotein using paraffin wax and cryostat sections; to compare c-erbB-2 expression in nonneoplastic and neoplas tic gastric tissues. Methods-Adjacent blocks of tumour and non-neoplas tic tissue from four gastrectomy specimens were put into a panel of 10 fixatives including acetone, B5, Bouin's fluid, Carnoy's fluid, buffe red formalin, formol dichromate, zinc formalin, 4% paraformaldehyde, p eriodatelysine-paraformaldehyde (PLP) and periodate-lysine-paraformald ehyde-dichromate (PLPD) before embedding in paraffin wax for sectionin g. Similar tissue blocks were snap frozen and cryostat sections were p ostfixed in these fixatives, either alone or in combination, before im munostaining. Results-In paraffin wax embedded sections the best fixat ive was PLP, and in frozen tissues the best results were obtained afte r fixation of cryostat sections in buffered formalin followed by cold methanol and acetone. Applying these fixatives to samples from a furth er 16 gastrectomy specimens, strong membrane staining of c-erbB-2 prot ein was found in the tumour in eight of 16 cases (50%) using paraffin wax sections, and staining was stronger in the better differentiated c arcinomas. For frozen tissues, positive membrane staining was found in all gastric adenocarcinomas, but differential staining intensity asso ciated with tumour differentiation could not be detected. Conclusions- These results indicate that fixation and paraffin wax embedding affect the results of immunohistochemical demonstration of c-erbB-2 in gastr ic cancer. The choice of fixative is critical in the demonstration and evaluation of c-erbB-2 protein expression by immunohistochemistry in gastric carcinomas. Staining results also vary depending on whether fr ozen or paraffin wax embedded tissues are studied.