Final answer:
Leukemia is a type of cancerous tumor that occurs in children and young adults and arises from bone marrow. It is characterized by an abnormal production of blood cells, particularly white blood cells. There are different types of leukemia, including acute and chronic leukemia.
Step-by-step explanation:
The type of cancerous tumor that occurs in children and young adults and arises from bone marrow is called leukemia. Leukemia is a cancer of the blood or bone marrow, where abnormal white blood cells are produced. It is characterized by an abnormal production of blood cells, usually white blood cells. There are different types of leukemia, including acute and chronic leukemia, which involve an overproduction of immature or mature leukocytes respectively.