Abstract
Although some benign breast lesions such as multiple intraductal papilloma have been pointed out as a risk factor for breast cancer, there is little documentation about trends in the incidence of benign tumors of the breast in Japanese women. The author conducted an epidemiological study using data abstracted from the Hiroshima Tumor Tissue Registry file, which includes cases of malignant and benign neoplasms in Hiroshima prefecture between 1973 and 1995. A total of 17064 cases of female breast tumor were registered in the file between 1973 and 1995. The registration rate for fibroadenoma of the female breast was 19.5 among females and peaked during the 5-year period 1983 - 1987, while the fibroadenoma registration rate in Hiroshima gradually decreased between 1988 and 1995. The registration rate for intraductal papilloma has risen substantially in Hiroshima, with about a 5-fold increase among females between 1973 and 1995. The mean proportion of fibroadenoma cases accompanied by malignant tumors of the breast was 1.85%, and there was no significant change in the mean proportion between 1973 and 1995 (P = 0.17). On the other hand, the mean proportion of intraductal papilloma cases accompanied by malignant tumors of the breast gradually rose with about a 14-fold increase among females between 1973 and 1995. The significance of intraductal papilloma as a risk factor for breast cancer may have increased.