Many people think of cancer as a single disease, and for many years the only treatment was to cut out tumor tissue that could be seen. However, the history of cancer is that we have gradually subdivided malignancies into multiple categories. First was the site of origin (lung, colon, breast, and so on); the second was based on what it looked like under the microscope (an adenocarcinoma vs a squamous cancer, for example); and a third was the extent of the tumor – whether it stayed in the organ of origin or spread to lymph nodes, lung, bone, and other organs.
Therapy regimens gradually evolved to treat each of these categories differently, with standard treatments tailored to the specific situation, and this type of increasingly customized therapy has been extremely important...