False negative mammograms causing delay in breast cancer diagnosis.

Eighty patients with negative mammograms and proven breast cancer are described. The incidence of negative mammograms is 5 to 7% of all breast cancer in Northern Alberta. In 30 patients, immediate biopsy because of clinical abnormality, and mastectomy, revealed only 3.3% axillary node involvement. The remaining 50 patients gave a history of finding a lump and then had a negative mammogram. Biopsy was delayed for a mean of 45 weeks. Their incidence of axillary node involvement was 42%. The mean age of both groups of patients was seven to eight years younger than the mean for all breast cancer patients. The implications of such delay on prognosis and survival are obvious. More public and medical education is needed.