Lymphomas and Microarray Research
One of the first discoveries of cancer subtypes was in a blood cancer called diffuse large B cell lymphoma (the most common subtype of non-Hodgkin's lymphoma). Using a chip that contained fragments of 18,000 genes, researchers found two distinct cancer subtypes. These cancers looked the same under the microscope, but had different patterns of gene activity.
The subtypes were different in other ways, too. For one thing, they arose from different types of cells. Tumor cells of one cancer subtype arose from less differentiated ("younger") lymphocytes, while the other subtype arose from more differentiated ("older") lymphocytes.
There was also a survival difference between the two types. About 75 percent of the people with the "younger" subtype responded to chemotherapy, compared with only 25 percent of the people with the "older" subtype.