Leukaemias Flashcards
What is haematopoiesis?
The formation of blood cellular components, which are all derived from haematopoietic stem cells
What are the two main progenitor cells in haematopoiesis?
Common myeloid progenitor
Common lymphoid progenitor
What cells do myeloid progenitors give rise to?
Erythrocytes
Mast cells
Myoblasts
What cells do lymphoid progenitors give rise to?
Natural killer cells
T lymphocytes
B lymphocytes (and thus plasma cells)
What cells do myoblasts give rise to?
Basophil
Neutrophil
Eosinophil
Macrophages
From what progenitor has a myoblast differentiated?
Common myeloid progenitor
Where does haematopoiesis take place in adults?
The areas producing blood cells are the pelvis, spine, ribs, cranium, and proximal ends of long bones (bone marrow)
How are haematological neoplasms categorised?
Historically, hematological malignancies have been most commonly divided by whether the malignancy is mainly located in the blood (leukemia) or in lymph nodes (lymphomas).
What are characteristic features of acute haematological neoplasms?
Predominantly immature cells
Rapidly progressive and aggressive; fatal within days to week
What are characteristic features of chronic haematological neoplasms?
Predominantly mature cells
Indolent and slowly progressive; patients can live with the disease for a long period of time
What is myeloma?
Malignant disease of plasma cells
What are the four main leukaemias?
- Acute myeloid leukaemia
- Acute lymphoblastic leukaemia
- Chronic myeloid leukaemia
- Chronic lymphocytic leukaemia
What is the most common age group for acute lymphoblastic leukaemia?
Childhood (2-5 years)
What is the most common age group for chronic lymphocytic leukaemia?
Elderly
How is leukaemia diagnosed?
Leukaemia can be diagnosed by examination of a stained slide of peripheral blood and bone marrow, but immunophenotyping, cytogenetics and molecular genetics are essential for complete subclassification and prognostication
How would you investigate the degree of maturity of the leukaemic clone?
Expression of cytosolic enzymes and expression of surface antigens
What is the cause of acute leukaemia?
- Genetic syndromes
- Environmental risk factors
- Radiation
- Prior chemotherapy
- Prior infections
- drugs (benzene) - KMT2A mutation
From what cell does acute lymphoblastic leukaemia develop?
Lymphoid blast
ALL emerges when a single lymphoblast gains many mutations to genes that affect blood cell development and proliferation
What characteristic genetic changes need to have to increase the chance of developing leukemia?
Chromosomal translocations, intrachromosomal rearrangements, changes in the number of chromosomes in leukemic cells, and additional mutations in individual genes
How is C-Myc implied in leukemia?
“An example of this includes the translocation of C-MYC, a gene that encodes a transcription factor that leads to increased cell division, next to the immunoglobulin heavy- or light-chain gene enhancers, leading to increased C-MYC expression and increased cell division”
What does immunohistochemical testing in acute lymphoblastic leukaemia reveal?
TdT or CALLA antigens on the surface of leukaemic cells
Where do leukemias often metastasise to?
Lung, liver, spleen, lymph nodes, brain, kidneys, and reproductive organs
What is a histological marker for the myeloid lineage?
myeloperoxidase (MPO)
What genetic diseases are associated with leukaemias?
Fanconi anaemia, ataxia telangiectasia and Li–Fraumeni syndrome
What is the median age of onset for acute myeloid leukaemia?
65
What would blood tests for acute leukaemias show?
- Blood count –> Hb low, WBC raised, platelets low
- Blast cells seen
- Bone marrow aspirate -> increased cellularity, reduced erythropoiesis, reduced megakaryocytes (replaced by blast cells)
- Chest X-ray. Mediastinal widening often present in T lymphoblastic leukaemia
- Cerebrospinal fluid examination. Performed in all patients with ALL, as the risk of CNS involvement is high. It is less critical in AML
What are the respective lineages established by immunophenotyping for the different types of acute leukaemias?
AML – CD33 or CD13, B lineage
ALL – CD10 and
CD19 and T lineage – CD3
How would you manage acute lymphoblastic leukaemia?
First line: Pegaspargase (chemotherapy)
In complete remission with minimal residual disease: Blinatumomab
What is a blast cell?
An immature precursor of myeloid cells (myeloblasts) or lymphoid cells (lymphoblast)
Rarely ever seen in normal individuals
If present, are highly suggestive of an acute leukaemia
How would you manage a relapsed acute lymphoblastic leukaemia?
Tisagenlecleucel
How is the Philadelphia chromosome implicated in cancer?
The Philadelphia chromosome is a cytogenetic anomaly that is manifested as a shortened version of human chromosomes 9 and 22.
Ph chromosomes are present in over 90% of chronic myelogenous leukemia (CML) patients and also in 25% of adult acute lymphocytic leukemia (ALL) patients.
How is the Philadelphia chromosome implicated in chronic myelogenous leukemia specifically?
Associated with 97% of cases
What, on a molecular level, does the Philadelphia chromosome do?
The molecular consequences of the translocation are that part of the Abelson proto-oncogene (c-ABL) normally present on chromosome 9 is translocated to chromosome 22, where it comes into juxtaposition with a region of chromosome 22 named the ‘breakpoint cluster region, it is is now a fused BCR-ABL protein which acts as a tyrosine kinase
BCR-ABL activates a cascade of proteins that control the cell cycle and inhibits DNA repair