Cancer as a systemic disease.

Theories on the nature of cancer may be classified into two categories. One regards cancer strictly as a local phenomenon while the second looks at cancer as a local manifestation of a systemic process or disease. Although the first dominates current medical thought, the theories of immunological surveillance and of protovirus-oncogene implicitly assume cancer to represent a local manifestation of a systemic process or disease. This is supported also by epidemiological data forwarded in the present paper. In order to clarify the exact meaning of a systemic disease, cancer and its manifestation are compared with arteriosclerosis and its sequelae. Arteriosclerosis could be regarded as a prototype of a systemic disease. It presents itself clinically solely by its local manifestations, like myocardial infarction or stroke. These local manifestations may be followed by secondary systemic sequelae like congestive heart failure. In the same context, it is proposed to regard cancer as one systemic disease which presents itself clinically by local phenomena like carcinoma, lymphoma and sarcoma. These local manifestations may lead further to secondary systemic sequelae like metastasis.