[Heterogeneity of breast cancer].

Breast cancer is in many aspects a heterogeneous disease. This becomes also evident in family studies. The families of 116 women with breast cancer with 50 years and less at diagnosis were compared to than of 161 breast cancer patients with 51 years and more with respect to breast cancer in the relatives. Younger breast cancer patients had more second degree relatives with breast cancer. Probands with a positive family history were on the average 10 years younger than probands with a negative family history. A positive family history increases breast cancer risk by 4.3 times for first degree relatives and by 2.3 times for second degree relatives in comparison to the general population. These results point to an etiological heterogeneity of breast cancer.