Immunohistochemical study of ras p21 expression in human gastric cancers and benign lesions

Expression of ras p21 in human gastric cancers, benign lesions and normal tissues was immunohistochemically evaluated by the avidin-biotin peroxidase complex (ABC) method with anti-ras p21 monoclonal antibody rp-28. Positive p21 immunoreactivity was shown in 23 (77%) of 30 gastric cancers, in 13 (48%) of 27 benign lesions and in 10 (22%) of 46 normal mucosa cases. Among them, strong staining was demonstrated only in 11 (37%) of 30 gastric cancers, but not in benign lesions and normal tissues. Cases showing more than 20% positive cell ratio were observed in 22 (73%) gastric cancers, in 11 (41%) benign lesions and 6 (13%) normal mucosa cases. Further, intracellular distribution of ras p21 is heterogeneous in gastric cancers, while it is homogeneous in benign lesions or normal tissues. The ABC method with rp-28 could be helpful for clinical differential diagnosis between gastric cancers and benign lesions by investigating three factors: staining intensity, positive cell ratio and intracellular distribution of ras p21.