rates may change as treatment protocols improve. for second remission (cr2), if achieved, both chemotherapy and transplant options are possible, and many physicians prefer transplant. prognosis bcr-abl positive acute lymphoblastic leukemia (all) has a 5-year survival rate ranging from 50% to 75%, in studies of the era of tyrosine kinase inhibitors. history the philadelphia chromosome was first discovered and described in 1959 by david hungerford at the lankenau hospital's institute for cancer research, which merged with the american oncology hospital in 1974 to create fox chase cancer center, along with peter nowell from the university of pennsylvania school of medicine. the genetic abnormality hungerford and nowell found was named after the city in which both organizations were located. and thus, this is a typical example of a medical toponym. hungerford was writing his doctoral thesis on chromosomes in a genetics lab at what was then the institute for cancer research at the lankenau hospital research institute, and detected a flaw in chromosomes from the blood cells of patients with leukemia. this founding observation was the first genetic defect to be linked with a specific human cancer. nowell was a pathologist at the university of pennsylvania who was also studying leukemia cells under the microscope when he noticed cells with this genetic flaw in the act of dividing. to his surprise, their chromosomes—usually an indistinct tangle—were visible as separate structures. in searching for an expert on chromosomes, nowell found hungerford locally at lankenau. while conducting his microscopic studies, hungerford furthered his observations with the discovery that certain leukemia cells had an abnormally short chromosome 22. subsequently, the mutation he observed became known as the philadelphia chromosome. in 1973, janet rowley at the university of chicago identified the mechanism by which the philadelphia chromosome arises as a translocation.