Evaluation of c-myc proto-oncogene in primary human breast carcinomas.

The expression of the c-myc proto-oncogene product was examined by immunohistochemistry in 11 normal breast tissues, 31 invasive and 14 non-invasive breast carcinomas. The c-myc product was detected in all breast carcinoma specimens and in seven of 11 normal breast tissues. Invasive tumors stained more frequently with the anti-myc monoclonal antibody (MAb) than non-invasive tumors, while the level of expression in normal breast tissue was much less than that in a breast cancer. Marked heterogeneity in the c-myc expression was seen among different tumors and within individual tumors. None of the eight invasive tumors with a high protein level of the c-myc showed evidence of gene amplification by Southern blot analysis.