Chronic myeloid leukemia

Studying hematopathology can be a challenge. There are so many new words and concepts that it can seem overwhelming at times. Here are some questions and answers that may help further your understanding of chronic myeloproliferative disorders.

Q. Are all chronic proliferative disorders caused by abnormal stem cells?

A. All chronic myeloproliferative disorders (chronic myeloid leukemia, polycythemia vera, essential thrombocythemia, and chronic myelofibrosis) are disorders of abnormal (malignant) stem cells. The chronic lymphoproliferative disorders are not stem cell disorders (they are disorders of a particular stage of maturation of a lymphocyte).

Q. How do leukemic transformations of the different chronic myeloproliferative disorders happen? Are the transformations related to treatments (such as radiation and chemotherapy), or are they due to an abnormal stem cell?

A. Leukemic transformation of myeloproliferative disorders is not due to treatment; it’s due to a progression of the disease itself. All the chronic myeloproliferative disorders are disorders of stem cells (the lymphoproliferative ones are not, though), so as such, the malignant cells can “decide” to manifest as a young cells or mature cells. The chronic myeloproliferative disorders start out as proliferations of mature myeloid cells, and most of the time, they stay that way. But in some patients, as the disease progresses, the malignant clone can change – perhaps it acquires new chromosomal abnormalities, or somehow otherwise changes its maturation/differentiation capabilities – so that it starts manifesting itself as very immature cells (blasts).

Q. I know patients with polycythemia vera, essential thrombocythemia, and myelofibrosis are at risk of leukemic transformation. How come patients with CML are not?

A. They are – it’s just that in CML, the leukemic transformation is called “blast crisis”. Same thing, different name.

Q. Can all proliferative disorders share the risk of undergoing a Richter’s transformation?

A. No, only chronic lymphocytic leukemia (CLL) has the capacity to undergo Richter’s transformation.