On the Bimodal Age Distribution of Mammary Carcinoma

IN 1930-shortly after his death-a book written by von Pirquet was published. This treatise gave an analysis of the age distribution of a large number of malignant tumours, the mortality statistics having been obtained from the British Registrar-General. One of the interesting facts presented was a bimodal type of age distribution of mammary carcinoma: it was shown that the distribution was probably built up by two separate distributions, one having its highest frequency at about 50 years of age, the second type (a " Spiitkrebs ") being most frequent at about 70 years. After World War 11 attention to this peculiar feature was drawn again by Jacobsen (1946) and by Clemmesen (1948) who had been working with morbidity figures of the Danish Cancer Registration. From many sides confirmation of the bimodal type of age distribution was published: Anderson et al. (1950) gave morbidity figures from Connecticut, U.S.A., Maisin and Langerock (1955) presented graphs of Danish, Swedish and French material at the Congress of Geographical Pathology held at Washington ; at the Perugia Symposium on mammary