Elevated ras oncogene expression correlates with lymph node metastases in breast cancer patients.

The protein product of the ras cellular oncogene(s) (p21) was assayed in primary breast carcinomas from two groups of patients who had different axillary lymph node status. Using an immunohistochemical assay, the intensity and percent of neoplastic cells demonstrating ras p21 antigen staining were significantly higher in the primary tumors from patients with lymph nodes positive (LN+) for malignancy (20 patients) compared with the lymph node negative (LNO) group (21 patients). The expression of p21 also correlated with tumor size. Age and estrogen receptor status did not influence p21 staining. The antigen expression of p21 was similar in intensity and distribution in the primary tumor and regional lymph node metastases. Enhanced expression of p21 in primary breast cancers that metastasize to regional nodes indicates that ras p21 may be a determinant of the malignant potential of breast cancer cells and may represent a new class of more biologically relevant tumor markers.