Cancer is not exclusively a modern disease, and paleopathological evidence of many of its forms has been found in ancient human remains. Even so, the evidence from thousands of prehistoric and ancient remains, such as fossils, mummies, and skeletons, suggests neoplasms were not common until after the medieval period in Europe. Investigation of Egyptian mummies suggests malignancies were rare, although multiple melanoma cases have been well documented, and also nasopharyngeal carcinoma, which is readily identifiable through damage to the skull. Hippocrates made the distinction between malignant and benign cancers in the fifth century BC. Although malignant cancers are now usually referred to as malignant neoplasms, the term cancer is used here as it has a longer history in the research literature. At the end of the 18th century in England, there were early references to cancer as a form of “tubercle,” and only a few deaths were recorded in the “cancer” category in the London Bills of Mortality. In some cases the wasting may have been difficult to distinguish from the effects of tuberculosis for the purposes of recording cause of death. When national registration began in England and Wales, the term malignant tumors was already in use, although “carcinoma” was not formally distinguished from “genuine crude tubercle” until 1855. Pathologists sought to define the difference between cancer and tuberculosis, which occur in many of the same sites in the body, and the idea of an inverse relationship developed despite both occurring at the same time in a few cases. It is now usual to regard cancers as a group of diseases, differing widely in etiology, frequency of occurrence, and site of manifestation.

The underlying processes in cancer have long been regarded as linked with the cumulative effects of irritants and carcinogens. Burnet suggested that errors in the repair of DNA could explain associations between carcinogens and particular sites of cancer, such as radiation and skin cancer, cigarette smoking and lung cancer, naphthylamines and bladder cancer, radium salts in paints and bone sarcoma, and many others. The molecular-level process in “environmental cancer” could involve a carcinogenic agent entering cells and causing damage to the DNA, which can be repaired but with an increased risk of informational error and abnormal cells that can replicate out of control.