“It’s a cancer of the blood and the bone marrow,” said Dr. Dana Egan-Sherry, a pediatric hematologist/oncologist with Hasbro Children’s Hospital. Egan-Sherry is referring to Acute Lymphoblastic Leukemia, also known as A.L.L., the most common cancer in children. Justin Degnan, 14, of North Smithfield knows all about it. “Back in…