This is what a child’s blood cancer may look like under the microscope. ALL: Acute Lymphoblastic Leukemia. It’s more than just cells under the microscope; it’s a diagnosis that changes lives. ALL is a cancer of the bone marrow and lymphoid line, where immature white blood cells (lymphoblasts) multiply uncontrollably, crowding out healthy cells that your body needs to function. Under the microscope, you’ll see: Large lymphoblasts with high nuclear-to-cytoplasmic ratios Scant cytoplasm, fine chrom