Expression of p21 ras gene products in breast cancer relates to histological types and to receptor and nodal status.

Expression of the p21 product of the ras gene family was investigated in a series of 142 infiltrating primary breast tumors by two specific ras p21 monoclonal antibodies with an immunocytochemical technique. The majority of tumors demonstrated a varying number of positive cells. A significant association between p21 expression and tumor histotype was found: among ductal carcinomas the comedo variety was always positive; conversely, lobular tumors were more frequently negative. Nodal status was recorded for all patients. A significant difference was found in nodal status with respect to p21 expression: tumors with more than 50% positive cells were more often N+. Estrogen receptor (ER) status was determined in 77 tumors. Tumors with higher levels of p21 contained a high percentage of estrogen receptor positive cells. The present results show that p21 expression in human breast cancer could be a marker of tumor aggressiveness and might thus improve the predictive power of known prognostic factors such as estrogen receptor and nodal status.