During the Renaissance, beginning in the 15th century, scientists developed greater understanding of the human body. Scientists like Galileo and Newton began to use the scientific method, which later was used to study disease. Autopsies, done by Harvey (1628), led to an understanding of the circulation of blood through the heart and body that had until then been a mystery.
In 1761, Giovanni Morgagni of Padua was the first to do something which has become routine today – he did autopsies to relate the patient’s illness to pathologic findings after death. This laid the foundation for scientific oncology, the study of cancer.
The famous Scottish surgeon John Hunter (1728-1793) suggested that some cancers might be cured by surgery and described how the surgeon might decide which cancers to operate on. If the tumor had not invaded nearby tissue and was “moveable,” he said, “There is no impropriety in removing it.”A century later the development of anesthesia allowed surgery to flourish and classic cancer operations such as the radical mastectomy were developed.Source - American Cancer Society