Acute Leukemias and their Diagnosis, Acute Myelocytic and Acute Lymphocytic Leukemia

Sample

1. Blood in EDTA and fresh blood smear needed.
2. Bone marrow aspirate and biopsy are required.

Definition of acute leukemia

1. This is a malignant neoplasm of hematopoietic cells particularly stem cells.
2. There is diffuse infiltration of the bone marrow by these neoplastic cells.
3. These cells enter the blood and may infiltrate the liver, spleen, lymph nodes and other organs.

Classification of Acute Leukemias

• On the morphology of the cells, these are divided into:

1. Acute lymphocytic leukemia (ALL)
2. Acute myelocytic leukemia (AML)
3. The following diagram shows how these leukemias develop from the blast cells.

Pathophysiology

1. The malignant transformation is at the level of pluripotential cells like stem cell and these are the committed stem cells, called stem cell disorder.
2. There is abnormal proliferation, monoclonal expansion, and decreased apoptosis of these cells leads to the replacement of normal bone marrow cells by these malignant cells or immature cells.
3. Acute Leukemias has little or no maturation and may see mainly blast cells.
   1. Acute Leukemias are diagnosed on the percentage of blast cells in the bone marrow.
   2. 30% or more blast cells are needed to classify the disorder as acute leukemia.
      

      Type of cells	% of the cases	FAB subtype
      Pre B- cells ALL	75	L1 and L2
      B-cell ALL	5	L3
      T – cell ALL	20	LI and L2

Acute Leukemias signs and symptoms

1. Appears suddenly.
2. The patient may have weakness and fatigue.
3. The patient may have a low-grade fever.
4. There may be bruising and mild bleeding from the gums.
5. There is bone pain due to the expansion of the marrow.

Diagnosis of Acute Leukemia

1. These are more common in the younger age group.
   1. These are more frequent in children.
   2. Mostly seen before the age of 20 years.
2. Onset is an abrupt and fatal outcome.
   1. There is a fever.
3. There is a rapid development of anemia.
   1. There is normochromic and normocytic anemia.
   2. May see nucleated RBCs.
4. There is thrombocytopenia.
   1. May see petechiae and purpura in the skin and mucous membranes.
5. Leukocytes count is variable.
   1. Mostly leucocyte count is less than 100,000/cmm.

Acute Myeloid Leukemia (AML)

1. Pathogenesis:
   1. There are primary AML  which appears to appear de novo.
   2. Secondary AML which develops from:
      1. The myelodysplasia.
      2. Other hematological diseases such as myeloproliferative diseases.
      3. Or following previous treatment with chemotherapy.
2. Age: This is seen during the first month of life and then in the later age group.
   1. 10 to 15% of cases found in the children.
   2. If there is exposure to high energy radiation in early childhood life have increased risk for developing T-cell acute lymphoblastic leukemia.
3. Sex: More common in males than women. Male: female ratio is 3:2.
4. Signs and symptoms:
   1. Mostly these patients present with a varying degree of bone marrow failure.
   2. So clinical symptoms and signs are due to anemia, leukopenia, thrombocytopenia, and infections.
      1. About 1/3 of the patient have bruises and hemorrhages.
      2. About 1/4 of the patients have severe infection involving the lungs, soft tissue, or skin.
      3. Splenomegaly and hepatomegaly are not common and seen in<25% of the cases.
      4. Lymphadenopathy is even less common.
      5. Gingival hypertrophy or skin infiltration by the tumor occurs in 50% of the patients with monocytic leukemia.
      6. Acute promyelocytic leukemias are more commonly seen with severe bleeding from the DIC.
   3. Fever and fatigue are present in most of the patient.
   4. Acute promyelocytic leukemia (M3) causes disseminated intravascular coagulopathy (DIC) and bleeding.
   5. Acute myelomonocytic leukemia (M4) and acute monocytic leukemia (M5) causes gum hypertrophy.
   6. There may be tumor infiltrate of AML called granulocytic sarcoma (Chloroma), skin and the bone particularly sternum, ribs, and orbit are common sites.  Myeloid sarcomas may involve any organs.
   7. These patient may have respiratory distress due to leukostasis within the pulmonary vasculature.
   8. There may be retinal hemorrahe due to thrombocytopenia.
5. Classification:
   

   French-American-British (FAB) Classification of Acute Myelocytic Leukemia

   M0	Acute myeloblastic leukemia. Blast cells lake cytologic and cytochemical markers of the myeloid series cell. But express myeloid series lineage antigens. 2 to 3% of AML. Sudan black and myeloperoxidase stain are negative. express CD13 and CD33 antigen-positive on the surface.
   M1	Acute myeloblastic leukemia without differentiation. Undifferentiated myeloblastic. No cytoplasmic granules may see few. Only 3% of the cells are myeloperoxidase positive. Auer rods are common. These are 20 % of AML. Acute myelocytic leukemia M1
   M2	Also called AML with maturation. Differentiated myeloblastic (30 to 89%) cells and sparse granules in the cytoplasm. Myelocytes and promyelocytes are predominant. Auer rods are common. Cytogenetics show t(8;21)and (q22;22q). These are 30% of the AML. Acute myelocytic leukemia M2
   M3	Acute Promyelocytic Leukemia. Granules are typical of promyelocytic morphology, these are azurophilic. Blast cells contain prominent granules, nuclei are bilobed or kidney-shaped. Auer rods are many. These are strongly myeloperoxidase positive. Cytogenetics show t(15;17), t(11;17), and (q22;q11-12). These are 5 to 10 % of AML. Acute myelocytic leukemia M3
   M4	Acute Myeloid Monoblastic Leukemia. The mixed population of myeloblastic (>30%), and monocytic (>20%) morphology. Auer rods may be seen. These are 20 to 30% of AML. Acute Myelocytic leukemia M4
   M5	Acute Monoblastic Leukemia. Pure monoblastic cells. Monoblast and promonocytes predominate constitute >80%. Cytogenetics show t(9;11), (p22;q23), and t(11;q23). These are 10% of the AML. Acute myelocytic leukemia M5
   M6	Acute Erythroleukemia. Predominantly immature erythroblast >50%, and can see multinucleated megaloblastoid erythroblast.  Erythroblast cells are strongly PAS-positive. Myeloblasts are 30% or more.  These are 5% of AML. Acute erythroleukemia M6
   M7	Acute Megakaryoblastic leukemia. Megakaryocytic  Cells small and large size with shaggy borders that may show some budding. There is a high N/C ratio. Platelet peroxidase and platelets antibodies are often positive. Cytogenetics show t(1;22), and (p13;q13). These are 1% of AML. Acute myelocytic leukemia M7

6. Lab. findings : 
   1. WBC count is variable. 25% of the patient has >50,000/cmm, 25% has <5000/cmm and 5 to 10% has count between 5000 to 10,000/cmm.
      1. Count >100,000/cmm is repoted in <10% of the patients but these patienst have severe CNS or respiratory diseases due to leukostatsis.
      2. In these patients leukopharesis and chemotherapy may be life saving.
   2. WBC morphology. These are morphologically abnormal and immature cells.
      1. 20% or more of the blast cells in the bone marrow as diagnostic of AML.
      2. The peripheral blood smear may show blast cells in 85 to 90% of the cases.
      3. FAB divide AML into:
         1. M1, M2, and M3 with granulocytic differentiation.
         2. M4, M5 with at least 20% monocytoid appearance.
         3. M6 with a high proportion of erythroblasts.
         4. M7 with predominantly megakaryoblasts.
         5. M0 with minimal myeloid differentiation. This needs immunohistochemical stains for the diagnosis. These cases have myeloid antigens on their surface and myeloperoxidase activity is negative.
   3. Uric acid in 50% of the cases is raised which indicates increased cells turnover.
   4. Lactate dehydrogenase (LDH) about 50% show raised a level. This is not as common as in ALL.
   5. Bone marrow shows >20% blast cells. Promyelocytes are numerous particularly in M3.
      1. Auer rods can be seen in the cytoplasm.
      2. Cytochemical stains, peroxidase reaction and Sudan black are positive.
   6. Nucleated RBCs may be seen.
   7. Platelet count may be low and may see count between 30,000 to 100,000/cmm. In some cases may be <20,000/cmm.
   8. Coagulation abnormalities are also seen. PT, PTT and Thrombin time are prolonged.
7. Treatment: This is supportive and the specific treatment for AML.
   1. Stem cell transplantation, autologous transplantation may be done. But because of the toxicity overall no benefit.
   2. The treatment of patients over 70 years of age of AML is poor because of primary disease resistance and poor tolerability of intensive treatment.
      1. Death in the old people is usually from hemorrhage, infections, and failure of the heart, kidneys, or other organs as compared to the younger patients.
8. Prognosis:
   1. 50% of children and young adults may have a long-term cure.
   2. Recently with the newer advanced chemotherapy, the prognosis in the 60 to 70 years of age is better.
   3. Cytogenetics abnormalities and initial response to the treatment are the major predictors for the prognosis.
   4. AML overall complete remission is 60 to 70% and disease-free survival is 20 to 40%.
      1. <60 years complete remission is 70 to 80% and disease-free survival is 40%.
      2. >60 years complete remission is 45 to 55% and disease-free survival is 5 to 10%.
         

         Clinical parameters	Good prognosis	Poor prognosis
         Age	<60 years	>60 years
         Onset of AML	Primary	Secondary
         BM response to remission induction	<5% blast cells after one course of chemotherapy	20% blast cells after the first course of chemotherapy
         Cytogenetics	t(15;17), t(8;21), inv(16), NPM mutation	t(6;9), 11q23, abn(3q), deletion of chromosome 5 or 7

 Acute Lymphoblastic Leukemia (ALL)

1. Age:  ALL constiture 20% of the adult leukemia and these are more common in the children.
   1. This is most common in childhood. Mostly occur before the age of 4 years. The peak is between 2 to 10 years.
   2. These are rare after the age of 30 years.
   3. These are most common in children and young adults.
   4. The second peak may be seen in the middle and old age groups.
   5. L3 leukemia is most common in developing countries and may be associated with the infection by the Epstein-Barr virus in the younger age group.
   6. Children with trisomy 21 (Down’s syndrome) have increased risk for the childhood acute lymphocytic and also acute myelocytic leukemias.
2. Signs and symptoms:
   1. Onset is sudden. There is no preleukemic stage.
      1. Symtoms are present only for few weeks before the diagnosis.
   2. There are fatigue and fever. There is mailase, lethargy, and weight loss.
   3. There may be bleeding and infections.
   4. There is an enlargement of lymph nodes, spleen, and liver are more common than the AML affecting 50% of the adults.
   5. There may be involvement of the central nervous system (CNS) in 5 to 10% of the cases. This shows as leukemic meningitis.
      1. Cranial nerve palsy more common in the 6th and 7th nerves.
      2. There is headache and papilledema due  meningeal involvement and the obstruction of the outflow of CSF.
   6. Bone pain is due to the infiltration of the leukemic cells.
   7. Retinal hemorrahge is due to thrombocytopenia.
   8. Chest X-ray shows thymic mass in 10 to15% of the adults.
3. Classification:
   

   FAB (French-American-British) classification of Acute Lymphocytic Leukemia

   L1	Lymphoblasts with uniform, round nuclei, and scant cytoplasm. Nucleoli are not prominent.
   L2	More variable lymphoblast and cytoplasm is abundant. Nucleoli are large and may see one or more nucleoli.
   L3	Lymphoblasts with fine nuclear chromatin and blue to deep blue cytoplasm that contains vacuoles. Lymphoblast is large and has prominent nucleoli and these are one or more than one.

4. Lab. Findings:
   1. WBC count is variable from very high to low count.
   2. There are anemia and thrombocytopenia.
5. Bone marrow: Very few leucocytes are seen.
   1. Difficult to find normal WBCs or RBCs in the bone marrow.
   2. Characteristically there are blast cells.
   3. Auer rods are absent.
   4. Sudan’s black and peroxidase reactions are negative.
   5. Morphology of the cells:
      

      L1	Small uniform blast cells
      L2	Larger and more variable size of the cells
      L3	1. Uniform cells with basophilic and sometimes vacuolated cytoplasm, typical of Burkitt’s lymphoma. 2. Philadelphia chromosomes-positive acute lymphoblastic leukemia and t(8;14) found.

6. Treatment:
   1. The aim is to restore the normal function of the bone marrow by multiple chemotherapy drugs.
   2. Typically four drugs e.g. vincristine, prednisone, daunorubicin, L-asparaginase, and cyclophosphamide are used for induction and remission.
   3. 80 to 90% of the adult entres complete remission.
   4. around 30 to 50% will be alive free of disease for 3 years.
7. Prognosis:
   1. Patients with count >30,000/cmm have a shorter duration of the remission than patients with lower count.
   2. Older age >60 years is not a good favorable factor.
   3. Other factor which matters the prognosis are:
      1. Circulating blast cells %.
      2. The degree of bone marrow involvement.
      3. The presence of splenomegaly, hepatomegaly, and lymphadenopathy.
      4. LDH level.
      5. Involvement of the CNS at the time of diagnosis.
      6. Time needed to get the remission for 4 to 6 weeks.
   4. All ALL overall 80 to 90% have complete remission and disease free survival is 30 to 40%.
      1. T-ALL 90 to 95% have complete remission and isease free surval is 60 to 65%.
      2. Presursor B-Cell ALL has complete remission of 75 to 85% and disease free surval is 30 to 40%.
      3. ≥60 years complete remission of 75 to 80% and disease free surval is 10 to 25%.

Difference between Acute Myelocytic Leukemia and Acute Lymphocytic Leukemia

Characteristic Features	Acute Myelocytic Leukemia	Acute Lymphocytic Leukemia
Origin of the cells	Myeloid series cells	Lymphoid  series cells
Features of Blast cells	Large in size,	Small in size
	Cytoplasm is moderate	Cytoplasm is scanty
	Chromatin is fine and lacy	Chromatin is dense
	Nucleoli are prominent and >2	Nucleoli are indistinct and <2
Auer rods	Present	Absent
Sudan black and peroxidase	Positive	Negative
Bone marrow	A mixed population of myeloid cells and blast cells	Mainly blast cells and very few  WBCs or RBCs
Leukocyte Alkaline phosphatase (ALP)	Positive  (differentiate CML from the leukemoid reaction.	Negative
Periodic Acid-Schiff (PAS)	Positive in Erythroblast in M6 leukemia	Positive (block patterns) in L1 and L2 Negative in L3

Test value for the layman:

1. A blood examination is advised if the patient has a high TLC.
2. If the patient has anemia.
3. If the patient has enlarged lymph nodes.
4. In the case of patients has a fever and weakness.

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