Analysis of C-myc messenger-RNA expression in primary breast carcinomas with clinical follow-up.

The level of c-myc messenger RNA was measured in 105 primary breast carcinoma samples and matched normal breast tissue from the same patients. Only tumors showing a greater than 2-fold increase in c-myc levels were considered to be overexpressed. Overexpression of c-myc mRNA was identified in 27.6% of tumor samples analysed and was significantly correlated with mitotic grade (p=0.05) and intense lymphocytic infiltrate (p=0.026) but not with other clinical and pathological variables such as size, necrosis, lymph node involvement, estrogen or progesterone receptor status, menopausal status, age or staging of the patients and increased risk of relapse or overall survival. Approximately 25% of the tumors contained overexpression of c-erbB-2 mRNA and simultaneous overexpression of the two oncogenes was seen in only five samples. Disease-free survival was significantly shorter in these patients (p=0.02) and this reduction remained significant after adjustment for nodal status. However, simultaneous overexpression of c-myc and c-erbB-2 did not improve significantly the prediction of risk of death.