Final answer:
Leukemia is the cancerous disease that causes an overproduction of leukocytes and their undifferentiated precursors in the blood, and is a type of blood cancer commonly starting in the bone marrow.
Step-by-step explanation:
The cancerous disease referred to in the question is leukemia, which is characterized by the presence of large numbers of leukocytes and their undifferentiated precursors being released into the blood. Leukemia is a type of blood cancer that typically starts in the bone marrow, leading to the overproduction of abnormal blood cells, usually white blood cells. It can affect different types of blood-forming tissues and is the most common cancer in children, though it often occurs in adults as well. There are various types of leukemia, depending on the type of leukocyte affected and the rate of progression; for example, myelocytic or lymphocytic, and acute or chronic leukemia. Patients with leukemia may experience symptoms such as fatigue, frequent infections, and excessive bruising or bleeding due to the dysfunctional nature of the abnormal cells.