35 Pathology #11 Acute Leukemias Farah Banyhany Dr. Sohaib Al- Khatib 23/2/16 1
Salam First of all, this tafreegh is NOT as long as you may think. If you just focus while studying this, everything will be fine. Always remember that you are capable of doing more than what you think. Today is your day, so be the best that you could ever be. There are 2 parts to this tafreegh. The first is the lecture itself (15 pgs) and the second is a review from the book (7 pgs). Let s start! During the previous lectures, we discussed lymphomas. Lymphomas are tumors of mature lymphocytes. Leukemias can be either acute or chronic. Acute leukemia is a tumor of immature cells (blasts/proliferation of precursor cells). It is divided into myeloid and lymphoid. The defect of acute leukemia is within the bone marrow or the thymus (for T lymphoblastic leukemia, its maturation occurs in the thymus). Acute leukemia can have blasts in the bone marrow, and these immature cells can later pass on to the circulation (peripheral blood). The lesion in this type of leukemia is in the precursors/blasts. Chronic leukemia affects mature cells, involving partial maturation. In chronic myelogenous leukemia, the maturation of granulocytes over other lineages takes place. Polycythemia Vera involves the maturation of RBCs, leading to an increase in hemoglobin over other lineages (Partial maturation). In between, there is myelodysplastic syndrome (acute leukemia and chronic myeloproliferative neoplasm). Anything that affects the precursors will lead to acute leukemia. Anything that affects the mature cells is either lymphoma or chronic leukemia. 2
As we know, a normal myeloblast can divide and differentiate. The concept behind leukemia is that the myeloblast will not be able to differentiate to reach maturity. It may differentiate partially, or not at all. It s not able to complete all stages of maturation. For example, in myeloblastic leukemia, the predominant cell is the myeloblast. In promyelocytic leukemia, the predominant abnormal cell is the promyelocyte. These cells will not be able to differentiate into Neutrophils. Therefore, a patient with leukemia is most commonly seen with anemia, cytopenia, and neutropenia. The marrow is hypercellular, meaning that it is compacted with cells. However, there is no maturation. You have precursors, but no differentiation or maturation. The difference between a normal stem cell/myeloblast and a leukemic blast is that the normal stem cell can differentiate whereas the leukemic blast cannot. In the normal marrow, you shouldn t have more than 5% of stem cells. However in leukemia it can reach to 20-30% of abnormal blasts. So, in erythroblastic anemia, the majority of cells are erythroblasts. In monoblastic leukemia (acute myeloid leukemia), the majority of cells are monoblasts. All of these are acute myeloid leukemias because the myeloid lineage can give erythroid cells, megakaryocytes, monocytes, and neutrophils. 3
Myeloid / Lymphoid disorders Lymphoid: chronic or acute -Acute lymphoid leukemia: also known as: lymphoblastic leukemia (ALL) -Chronic lymphoid disorders: lymphomas, chronic lymphocytic leukemia, small lymphocytic lymphoma Myeloid: chronic or acute -Acute: more than 20% of the cells in the marrow are primitive cells (blasts) acute myeloid leukemia. -Chronic myeloproliferative neoplasm/myelodysplastic syndrome: less than 20% of cells in the bone marrow are blasts. (Partial differentiaton / maturation) Polycythemia vera, myelofibrosis, essential thrombocythemia are examples of chronic myeloproliferative disorders. Can a chronic myeloproliferative/myelodysplastic disorder transform into a higher stage acute leukemia? Yes. A patient may first have Polycythemia vera and 5% blasts (chronic). After a follow up, the patient may develop acute bone myeloid leukemia with more than 20% blasts. So this patient will be diagnosed with acute myeloid leukemia because the amount of blasts has increased to 20%. Remember, 20% is the magic number. In acute lymphoid leukemia (lymphoblastic leukemia), the number of blasts is not precise like in acute myeloid leukemia, but it is generally 30%. So more than 30% in the bone marrow this is acute lymphoblastic leukemia. Acute Myeloid Leukemia o There are subtypes within this leukemia. There are AMLs with recurrent genetic abnormalities, AMLs with features of myelodysplasia (compact disease), and AMLs that are therapy-related. o Sometimes, a patient with lymphoma who is treated with chemotherapy will develop cytopenia. In the marrow there are more 4
than 20% blasts, so the patient will have acute myeloid leukemia due to chemotherapy. So generally, patients with any cancer (colonic, breast, etc.) can develop leukemia from chemotherapy. This is what we call a therapy-related AML. o So far we ve mentioned 3 types of AML above. The last type of AML is one that does not have any of the above features. It does not fulfill the criteria of having genetic abnormalities, no features of myelodysplasia, and is not therapy- related. Let s say there is a patient who has an AML with recurrent genetic abnormalities, like translocations. If the amount of blasts is less than 20% would he be treated as AML or CML? We know this: AML: >20% blasts CML: <20% blasts BUT, in this case, even if the amount of blasts is below 20%, this patient would be treated as though he has AML because of the genetic abnormalities. Case: A 25-30 year old patient was presented to you with cytopenia. What do you do? -CBC. -He is having symptoms of weakness, pallor, bleeding, fatigue, bruising. - Hemoglobin & platelet counts dropped Thrombocytopenia & anemia. - You do bone marrow biopsy and count the amount of blasts and it turns out 5
to be 10%. Is this acute? Well, we may think it is chronic because the amount of blasts is below 20%. But that doesn t stop there! Next, we must do a genetic study using cytogenetic or FISH analysis. The result shows that the patient has translocation (8; 21). In this case, you should treat the patient as if he has acute myeloid leukemia. - This is the significance of having subgroups for AML. If you find a translocation (genetic abnormality), but the blast count is less than 20%, you treat the patient as acute myeloid leukemia. The treatment and prognosis of AML differ from those of chronic myelogenous leukemia(cml) in part because the cellular differentiation is not the same; AML involves higher percentages of dedifferentiated and undifferentiated cells, including more blasts (myeloblasts, monoblasts, and megakaryoblasts). -Wikipedia The different subtypes of AML have varying prognoses. Those with AML of genetic abnormalities usually have a good prognosis. If AML is not specified, they will be classified according to their morphology. For specific types of AML, they are most preferably classified according to their cytogenetic abnormalities, not morphology. Morphology findings tend to be more subjective, whereas cytogenetic findings are more specific. When leukemias have normal cytogenetic findings, we can then classify them according to their morphology (erythroblastic/monoblastic leukemia). 6
FAB (French American British) classification of acute myeloid leukemia: Classification of myeloproliferative neoplasm: If you have a patient with AML, the peripheral blood CBC should show cytopenia and a decrease in blood components. How can a clinician diagnose a patient with myeloproliferative neoplasm? By doing a CBC there should be cytosis in one lineage and cytopenia in another lineage. Case: Patient with chronic myelogenous leukemia CBC WBC count is 50,000 (high) Most of the cells are Neutrophils Patient may also have anemia or thrombocytopenia. In myeloproliferative neoplasm, there is a partial maturation (maturation of one lineage over other lineages). The first thing to do in any patient if you are suspecting myeloproliferative neoplasm is to look for Philadelphia chromosome t(9;22) Chronic Myelogenous Leukemia. Whenever the differential diagnosis is of a myeloproliferative disorder, you should rule out CML first (myeloproliferative spasm) by looking for t(9:22). CML has its own treatment, different from polycythemia vera and essential thrombocythemia. 7
There are four main myeloproliferative diseases, which can be further categorized by the presence of the Philadelphia chromosome: -Wikipedia Myeloproliferative neoplasms are classified according to the presence/absence of the Philadelphia chromosome. If this chromosome is present CML. If this chromosome is absent Polycythemia Vera or Essential Thrombocythemia/thrombocytosis. Myelofibrosis then develops secondary to PV or ET. Myeloid (NON-lymphoid) neoplasm: -Acute myeloid leukemia -Myeloid dysplastic syndromes in between, having features of acute leukemia and myeloid proliferative neoplasms. -Chronic myeloproliferative disorders 8
Leukemia deals with precursors (B/T lymphoblastic leukemia). Leukemias may have double positivity or double negativity. For example, in T lymphoblastic leukemia, lymphoblasts are either CD4+/CD8+ or can be negative for both. For lymphomas, there is either CD4+ lymphoma or CD8+ lymphoma because lymphoma arises from mature cells whereas leukemia arises from immature cells. The stages of maturation starts with double negativity/positivity (immature) then in the peripheral blood there will be CD4+ OR CD8+ (mature). Antigens / markers expressed on cells allow us to differentiate between a mature and immature cell. Sometimes leukemia will look like lymphoma. So according to the markers of maturity, we can distinguish between them. Markers of immaturity: TdT (nuclear), CD 34 (cytoplasmic), CD 117 Blasts are positive for the myeloid-associated markers CD13, 14, CD15 or CD33, CD34 and negative for B or T lineage marker (CD3, CD10, CD19 and CD5). Taken from an online pdf, check it out! ~ http://cdn.intechopen.com/pdfs-wm/25114.pdf ~ Lymphoid stem cells (primitive) found in the bone marrow produce lymphocytes. It expresses TdT, and CD 34 on the surface. However the mature cell does not have these markers (TdT, CD 34). Let s say you have a peripheral blood sample with a lesion. You look at the cells in the sample and see that they express CD34, CD19, and CD20. The cells are blasts (immature) and are abnormal because they re expressing mature and immature cells. So, this is lymphoblastic leukemia. * If it expresses CD34, CD19, CD20 B lymphoblast. * If it expresses CD4, CD8, CD3, TdT T lymphoblast. T & B lymphoblastic leukemia can t be easily differentiated from each other just by looking at them; so in conclusion, we look for markers of immaturity. CD 10,19, 20, 21, 22, 23 B cell markers CD 3, 4, 8, 5, 2, 7 T cell markers 9
CD3 a specific T cell marker. If you have a lymphocyte expressing CD3 and CD10, this is a T lymphocyte. CD3 is the only specific T cell marker. CD2 is not specific; it is seen on a T cell marker. CD5 is not specific because it is seen in both T and B lymphocytes (small subset of B cells mantle cells). Mantle cell lymphoma is CD5+. CD8 is a cytotoxic T cell. CD13, CD14, CD15 myeloid monocytic markers CD34 stem cell marker CD30 + in Hodgkin cells, Reed Sternberg cells, and activated B lymphocytes CD45 (+) common to all T / B lymphocytes, except Hodgkin cells (RS cells) *So when is CD45 (-)? In Hodgkin cells (RS cells) * CD45 is used when in this case: We take a biopsy from a patient, and the tumor looks poorly difffernetiated. Is it lymphoma, leukemia, or poorly differentiated carcinoma? Do CD 45. If the cells are positive for CD45, then it is a lymphoid neoplasm. * In conclusion, CD45 is a common lymphocyte marker. 10
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If you are suspecting a patient with leukemia what should you do? First, start with taking a peripheral blood sample and a bone marrow biopsy. You find that cytopenia is very significant. You have to investigate this instead of just sending the patient home. You have a 6 year old presented to you with anemia: Hgb= 6 g/dl Platelet count = 50, 000 Do bone marrow biopsy. Peripheral blood: microcytic hypochromic anemia, no platelets. The lesion is in the bone marrow. The minimum requirements for someone with cytopenia are to do full blood count, bone marrow biopsy, and cytogenetic analysis. Take a bone marrow biopsy from the marrow of the patient. It is usually taken from the sternum or iliac crest in adults. This is done by using a needle and placing it within the marrow. The reason why we take a biopsy from these 2 bones is because the residual sites of the active marrow are found there. Biopsy from the sternum is more painful and has more complications than the iliac crest. After taking a sample, you aspire it with fluid (bone marrow aspirate). This will look like a peripheral blood sample but it actually represents the marrow. 2 Biopsies: 1. Bone marrow trephine needle biopsy aims at the bone, arrangement of cells, and the cellularity of the marrow. 2. The aspirate is just fluid, and examines the cells in thin spread. The details of the cells here are easier to examine and is used for flow cytometry. 12
The bone marrow is composed of adipose tissue and cells. This is important because you have to know the normal cellularity and the actual cellularity by examination. Normal cellularity = 100- age (+- 10) *This marrow (in the image) is normocellular for a 50 year old patient but hyper cellular for an 80 year old patient because the estimated cellularity shows that half of the marrow is fat and half of it is cells. So, this marrow is 50% cellular. So it is considered normocellular for a 50 year old. For an 80 year old, it s hyper cellular. 13
Leukemia has a 100% cellularity abnormal, regardless the age. So in this photo, the marrow is completely abnormal. This is seen in acute myeloid leukemia, myeloproliferative neoplasms, and myelodysplastic syndrome. In leukemia, the marrow is replaced by blasts (primitive cells). In a normal peripheral blood, there are RBC, platelets, and no precursors. You can see normal lymphocytes, and its size is almost 2x the RBC. It is round and smooth, and has a dark, clumped chromatin. Here, we see a blast. Normal lymphocytes are usually larger than RBCs by 2X. But here, its size is larger by 4-6X. The chromatin is not dark and is dispersed. Large amount of blasts in the blood and more than 20% in the bone marrow means that this is a lymphoblastic leukemia or acute myeloid leukemia. 14
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Here, you ll find extra information from the book, for anyone who s interested. It s more of a review to all that was mentioned above. BOOK CORNER: ROBBINS: Pages 444-448 Myeloid Neoplasms Arise from hematopoietic progenitors & give rise to clonal proliferations that replace the bone marrow. 3 categories: 1. Acute Myeloid Leukemia AML: Immature myeloid cells (blasts) accumulate in the marrow and replace normal elements; they frequently circulate the peripheral blood. 2. Myeloproliferative Disorders Neoplastic clone exhibits dysregulated growth. Involves the increase in formed elements (RBC / platelets / granulocytes) in the peripheral blood. 3. Myelodysplastic Disorders Disordered differentiation Dysplastic marrow precursors / peripheral blood cytopenias *Both myeloproliferative and myelodysplastic disorders can transform to Acute myeloid leukemia. *Some neoplasms have features of both myeloproliferative and myelodysplastic disorders. 17
Acute Myeloid Leukemia o Affects older adults (50 yrs.) o Closely resembles ALL & involves the replacement of the bone marrow elements with leukemic blasts. o Fatigue, pallor, abnormal bleeding, infections are symptoms in the newly diagnosed patients. o It is classified according to morphologic, histochemical, immunophenotypic, and karyoptypic findings. o Splenomegaly and lymphadenopathy occur to a lesser extent than in ALL. o AML is divided into 4 categories: - AMLs with genetic abberations - AMLs with dysplasia (which may arise from myelodysplastic syndromes) - AMLs occurring after genotoxic chemotherapy - AMLs without any of the above features. o Most tumors express a combination of myeloid associated antigens: CD13, CD14, CD15, CD64, CD117. o CD33 is expressed on pluripotent stem cells but is retained on myeloid progenitor cells. This marker distinguishes AML from ALL. 18
Myelodysplastic Syndromes o The bone marrow is replaced by the clonal progeny of a transformed multipotent stem cell that differentiates into red cells, granulocytes, and platelets. This occurs in an ineffective and disorderly manner. o Peripheral blood shows cytopenias. o The abnormal stem cell clone in the bone marrow is genetically unstable and can transform to AML. o Affects people within the ages of 50 70. o Cytopenias may lead to anemias and hemorrhage. o It has a poor response to chemotherapy. 19
Chronic Myeloproliferative Disorders o Involves the hyperproliferation of neoplastic myeloid progenitors that can terminally differentiate. This results in an increase in the formed elements of the peripheral blood. o Hepatosplenomegaly o This disorder is associated with activating mutations in tyrosine kinases. o 4 diagnostic groups: Chronic myelogenous leukemia (CML), polycythemia vera, primary myelofibrosis, and essential thrombocythemia. o CML has an abnormality in the BCR-ABL fusion gene, producing an active BCR- ABL tyrosine kinase. 20
Chronic Myelogenous Leukemia Affects adults between ages 25-60. It is always associated with the presence of a BCR-ABL fusion gene. (translocation 9;22) Fatigue, weakness, weight loss, splenomegaly What makes it distinct from other leukemias is the presence of the BCR- ABL fusion gene, which can be seen by karyotyping, FISH, or PCR assay. After some time, anemia, thrombocytopenia, cytogenicabnormalities, and the transformation into acute leukemia (blast crisis) may occur. This is the accelerated phase. Polycythemia Vera Excessive proliferation of erythroid, granulocytic, and megakaryocytic elements (panmyelosis). INCREASE IN RED CELL MASS / LOW LEVELS OF SERUM ERYTHROPOIETIN Increase in blood volume and viscosity Enlargement of liver and spleen Thromboses and infarctions are common in the heart, spleen, and kidneys. Hemorrhage abnormal platelet function. Usually occurs in the late middle age. Pruritus (itching), peptic ulceration, hypertension, headache, dizziness, GI symptoms, melena (GI bleeding), and hematemesis (vomiting of blood) are all symptoms. 21
Primary Myelofibrosis Extramedullary hematopoiesis (hematopoiesis in places outside the bone marrow like the spleen, liver, and lymph nodes. Splenomegaly and hepatomegaly This hematopoeisis is inefficient and disordered, leading to thrombocytopenia, anemia and neutropenia. Teardrop shaped red cells (poikilocytes) Nucleated erythroid precursors are present with immature white cells leukoerythroblastosis Primary Myelofibrosis 22
**SUMMARY - Myeloid Neoplasms** Myeloid tumors occur mainly in adults and fall into 3 major groups: Acute myeloid leukemias (AMLs) 1. Aggressive tumors comprised of immature myeloid lineage blasts, which replace the marrow and suppress normal hematopoiesis. 2. Associated with diverse acquired mutations that lead to expression of abnormal transcription factors, which interfere with myeloid differentiation. Myeloproliferative disorders 1. Increased production of formed myeloid elements, leading to high blood counts and extramedullary hematopoiesis. 2. Associated with mutations that activate tyrosine kinases, which mimic signals from normal growth factors. The most common pathogenic kinases are BCR-ABL & mutated JAK2. 3. All can transform to acute leukemia and to a spent phase of marrow fibrosis associated with anemia, thrombocytopenia, and splenomegaly. Myelodysplastic syndromes 1.Myeloid tumors characterized by disordered and ineffective hematopoiesis. 2. Manifest with 1 or more cytopenias and progress in 10% to 40% of cases to AML. Allow yourself to dream, And when you do, dream big. 23