There are many different types of leukemia, one of which is chronic myelogenous leukemia. This is one of the less common types. Because it is “chronic” it is slow to progress, compared to acute forms. Myelogenous, meanwhile, refers to the cell type that the cancer affects. So what is chronic myelogenous leukemia or CML? Essentially, there are two types: myeloid and granulocytic. Both are more common in adults and are very rare in children.