The bimodal age distribution of patients with mammary carcinoma.Evidence for the existence of 2 types of human breast cancer

T femaIe subjects with mammary carcinoma was observed in mortality statistics as early as 1930 by von Pirquetl3 and has since been confirmed by morbidity statistics from cancer registries in many European countries and the United States of America.l4,17The 2 peaks are in the 45-to 49-year age group and at about 65 years of age.As an example, Fig. 1 shows the age distribution of 10,047 patients with breast cancer registered in the Netherlands by the Central Cancer Registry, Amsterdam, during the years 1954-1960.1OAge-specific morbidity figures have been calculated for each year of the 1954-1960 period, the necessary population figures at the end of each year having been obtained from the Central Bureau of Statistics, The Hague.l5