Leukaemia is a blood cancer characterized by a rapid production of abnormal white blood cells called blasts. These malignant cells may be found in the bone marrow, where the blood cells are generated, and in the peripheral blood (i.e. in circulation within the blood vessels). As the disease progresses, the leukemic white blood cells swamp out the healthy blood cells, preventing them to perform their functions, like fighting infections or avoiding serious bleeding.
Like other cancers, there are many types and subtypes of leukemia. The most simple classification includes only four types of Leukaemia based on two parameters: evolution (chronic or acute), and cell lineage (myeloid or lymphoblastic/lymphocytic. Chronic leukemias typically have an indolent evolution, i.e. progress slowly over the years, whereas acute leukemias are more aggressive and may be fatal in few weeks.
For a correct diagnosis, physicians must take into account a lot of different information: the clinical features and the results from the morphology (shape, size and other characteristics of the malignant cells seen by microscopy), immunophenotyping (proteins expressed by the malignant cells seen by flow cytometry) and genetics analysis.
The different types of leukemias are associated with different symptoms, prognoses, treatments, and genetic causes. Part of making a correct diagnosis involves analyzing patients blood cells under a microscope after chemical staining, called a “blood smear”. Different leukemias are associated with different visual features of blood cells, such as their shape, color upon staining, and size.
There are several different types of leukemia:
Other types of blood and bone marrow malignancies include: