Page 379 - Textbook of Pathology, 6th Edition

consideration clinical, cytogenetic and molecular abnormalities 7. Chloroma or granulocytic sarcoma is a localised tumour- 363
in different types. These features can be studied by forming mass occurring in the skin or orbit due to local
multiparametric flow cytometry. infiltration of the tissues by leukaemic cells. The tumour is
2. WHO classification for AML has revised and lowered the greenish in appearance due to the presence of
cut off percentage of marrow blasts to 20% from 30% in the myeloperoxidase.
FAB classification for making the diagnosis of AML. WHO 8. Meningeal involvement manifested by raised intracranial
classifcation of AML is included in Table 14.4. pressure, headache, nausea and vomiting, blurring of vision
Both FAB as well as WHO classification schemes for AML and diplopia are seen more frequently in ALL during
are followed in different settings depending upon the haematologic remission. Sudden death from massive
laboratory facilities available in various centres. Moreover, intracranial haemorrhage as a result of leucostasis may occur.
most of the current clinical and laboratory data are based on 9. Other organ infiltrations include testicular swelling and
FAB grouping and hence detailed morphologic and mediastinal compression.
cytochemical features of various AML groups are given in
Table 14.5. Laboratory Findings

Clinical Features The diagnosis of AML is made by a combination of routine
blood picture and bone marrow examination, coupled CHAPTER 14
AML and ALL share many clinical features and the two are with cytochemical stains and other special laboratory
difficult to distinguish on clinical features alone. In approxi- investigations.
mately 25% of patients with AML, a preleukaemic syndrome
with anaemia and other cytopenias may be present for a few I. BLOOD PICTURE. Findings of routine haematologic
months to years prior to the development of overt leukaemia. investigations are as under (Fig. 14.14):
Clinical manifestations of AML are divided into 2 groups: 1. Anaemia. Anaemia is almost always present in AML.
those due to bone marrow failure, and those due to organ It is generally severe, progressive and normochromic. A
infiltration. moderate reticulocytosis up to 5% and a few nucleated
I. DUE TO BONE MARROW FAILURE. These are as red cells may be present.
under: 2. Thrombocytopenia. The platelet count is usually mode-
1. Anaemia producing pallor, lethargy, dyspnoea. rately to severely reduced (below 50,000/μl) but
2. Bleeding manifestations due to thrombocytopenia causing occasionally it may be normal. Bleeding tendencies in
spontaneous bruises, petechiae, bleeding from gums and AML are usually correlated with the level of
other bleeding tendencies. thrombocytopenia but most serious spontaneous
haemorrhagic episodes develop in patients with fewer
3. Infections are quite common and include those of mouth, than 20,000/μl platelets. Acute promyelocytic leukaemia
throat, skin, respiratory, perianal and other sites. (M3) may be associated with a serious coagulation Disorders of Leucocytes and Lymphoreticular Tissues
4. Fever is generally attributed to infections in acute leukae- abnormality, disseminated intravascular coagulation
mia but sometimes no obvious source of infection can be (DIC).
found and may occur in the absence of infection.
3. White blood cells. The total WBC count ranges from
II. DUE TO ORGAN INFILTRATION. The clinical subnormal-to-markedly elevated values. In 25% of
manifestations of AML are more often due to replacement patients, the total WBC count at presentation is reduced
of the marrow and other tissues by leukaemic cells. These to 1,000-4,000 /μl. More often, however, there is progres-
features are as under: sive rise in white cell count which may exceed 100,000/μl
1. Pain and tenderness of bones (e.g. sternal tenderness) are in more advanced disease. Majority of leucocytes in the
due to bone infarcts or subperiosteal infiltrates by leukaemic peripheral blood are blasts and there is often neutropenia
cells. due to marrow infiltration by leukaemic cells. The basic
2. Lymphadenopathy and enlargement of the tonsils may morphologic features of myeloblasts and lymphoblasts are
occur. summed up in Table 14.1. Typical characteristics of
3. Splenomegaly of moderate grade may occur. Splenic different forms of AML (M0 to M7) are given in Table
infarction, subcapsular haemorrhages, and rarely, splenic 14.5. In some instances, the identification of blast cells is
rupture may occur. greatly aided by the company they keep i.e. by more mature
4. Hepatomegaly is frequently present due to leukaemic and easily identifiable leucocytes in the company of blastic
infiltration but the infiltrates usually do not interfere with cells of myeloid series. Some ‘smear cells’ in the peripheral
the function of the liver. blood representing degenerated leucocytes may be seen.
5. Leukaemic infiltration of the kidney may be present and II. BONE MARROW EXAMINATION. An examination
ordinarily does not interfere with its function unless of bone marrow aspirate or trephine reveals the following
secondary complications such as haemorrhage or blockage features:
of ureter supervene. 1. Cellularity. Typically, the marrow is hypercellular but
6. Gum hypertrophy due to leukaemic infiltration of the sometimes a ‘blood tap’ or ‘dry tap’ occurs. A dry tap in
gingivae is a frequent finding in myelomonocytic (M4) and AML may be due to pancytopenia, but sometimes even
monocytic (M5) leukaemias.