Chronic Myeloid Leukemia (CML)
Introduction
- genetic hallmark is the presence of the BCR/ABL1 fusion gene
- 3 phases:
- chronic
- accelerated
- blast crisis
- prognosis: median survival time is approx. 5 – 7 years
Clinical signs
- at first asymptomatic
- anemia
- leukocytosis
- sometimes thrombocytosis
- later severe anemia, thrombocytopenia and splenomegaly (up to 10 kg)
Etiology
Caused by the BCR-ABL1 fusion gene, which in approximately
90 – 95% of all cases comes from reciprocal translocation
t(9,22)(q34,q11.2) — Ph chromosome.
Histology
- chronic phase: significantly hypercellular bone
marrow (usually 95 – 100%),
severe myeloid hyperplasia (markedly inreased myelopoiesis)
(M : E ration is 10 : 1 or more), predominantly myelocytes
and segment neutrophils, myeloblasts up to 10%, increased
numbers of small megakaryocytes with hypolobated nuclei,
residual erythropoiesis, varying grades of fibrosis
- accelerated phase: myeloblasts 10 – 19%, increased numbers of megakaryocytes organized in clusters,
expressive fibrosis
- blast crisis (acute leukemia): myeloblasts exceed 20% (AML),
sometimes transformation into acute lymphoblastic leukemia (ALL) or biphenotypic/bilinear leukemia
