Viruses and breast cancer. Introductory remarks.

Abstract

It has been shown that some breast cancers may have a long preclinic al existence. A host reaction may play a part in determining when preclinical becomes clinical cancer and on the subsequent course of the cancer. A study of breast cancer in mice has shown that it is a systemic disease produced by genetic factors hormones environmental factors and viruses. The virus B particle transmitted by mothers milk is the causative factor if other factors are also present. The virus is present in most organs of the mice including the blood mammary glands and milk long before clinical symptoms of cancer are found. The virus can be found in tumor cells grown in tissue culture but not in other cultured cells. Although the type B particle is regarded as the causative agent in mouse breast cancer its presence does not necessarily indicate future cancer development. However a correlation exists between high numbers of type B particles in milk of mice and a high incidence of breast cancer. Testicular tissues and spermatic fluid also contain virus and may infect the females. The type B particles are known as oncogenic or oncorna viruses. Breast cancers in mice have similarities as well as differences between the findings of neoplasia in women.