Ok, I will start with the definition and classification 😉

Wait, wait, you mean LEUKEMIA as a kind of WBC-related disease, right? Or something else? 🙄

DEFINITION:
A condition when WBC or leucocytes proliferate and grow out of control, thus its number is abnormally increasing compared to the normal level. It is caused by a cancer of the blood or blood-forming organ especially bone marrow. The large number of WBC, including the immature ones, mostly immature lymphocytes, then enter the peripheral blood stream (Stein, 2006).

CLASSIFICATION:
The major forms of leukemia are divided into four categories. Myelogenous and lymphocytic leukemia each have acute and chronic forms. The terms myelogenous or lymphocytic denote the cell type involved.

Acute leukemia is a rapidly progressing disease that affects mostly cells that are unformed or primitive (not yet fully developed or differentiated). These immature cells cannot carry out their normal functions.

Chronic leukemia progresses slowly and permits the growth of greater numbers of more developed cells. In general, these more mature cells can carry out some of their normal functions.

Thus, the four major types of leukemia are: acute or chronic myelogenous, and acute or chronic lymphocytic leukemia.

SUMMARY:
Major Types of Leukemia
* Acute Myelogenous Leukemia
* Acute Lymphocytic Leukemia
* Chronic Myelogenous Leukemia
* Chronic Lymphocytic Leukemia
(leukemia-lymphoma.org)