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INTRODUCTION

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CASE HISTORY • Part 1

A 16-year-old female presents with the recent onset of fatigue, headache, and repeated, difficult to control, epistaxis over the past week. She has been in excellent health and has no personal or family history of serious illness. She has 4 siblings.

Examination reveals pale conjunctiva and multiple petechiae on her lower legs. Abdominal examination suggests a slightly enlarged spleen. The remainder of her examination, including a neurological examination is normal.

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CBC: Hematocrit/hemoglobin 25%/8 g/dL

MCV - 90  fL MCH - 32 pg  MCHC - 31 g/dL

WBC count - 110,000/μL

Differential count:

Neutrophils 10%

Mature lymphocytes 3%

Immature blasts 85%

Monocytes/eosinophils/basophils <1%

Platelet count - 45,000/μL
SMEAR MORPHOLOGY

Normocytic, normochromic red blood cells with the occasional shift cell (polychromasia). Dominant population of blasts—moderately large cells with little cytoplasm and prominent nucleoli surrounded by an abnormal nuclear chromatin pattern; the few remaining neutrophils and lymphocytes appear normal. Platelets are reduced in number.

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Questions
  • What abnormality is apparent from the CBC?

  • What further studies are indicated?

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Acute lymphocytic leukemia (ALL) is a disease that primarily affects children. B-cell ALL is the most common malignancy in children under 15 years of age. The diagnosis and treatment of B-ALL in children constitutes one of the great success stories of hematology. Like Hodgkin disease, ALL has been approached with a combination of science and clinical insights that has produced a high frequency of true cures. An understanding of the principles of diagnosis and treatment of ALL serves as a model for the approach to all leukemias. Although the application of these principles to treat adult ALL is less likely to produce a cure, it is still the best approach to diagnosis and management.

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CLASSIFICATION

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The classification of ALL is based on a combination of morphologic (French-American-British [FAB]), immunophenotypic, and molecular/genetic characteristics.

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Morphologic Characteristics

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Similar to the FAB classification of the acute myelogenous leukemias, ALL can be divided into 3 classes—L1, L2, and L3—from the morphologic appearance of lymphocytes in the peripheral blood and marrow (Figure 25-1).

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FIGURE 25-1

Morphologic types of ALL. There are 3 major morphologic types of ALL. The small cell type L1 is most common in children but also occurs in adults. The L2 and L3 forms are more common in adults and have a significantly worse prognosis.

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With L1 disease the lymphocytes are uniformly small with round nuclei, little cytoplasm, and inconspicuous nucleoli. L2 disease consists of large, heterogeneous cells with more cytoplasm, irregular nuclei, and prominent nucleoli, whereas L3 disease is characterized by large cells with abundant, deeply basophilic cytoplasm, round nuclei, and prominent nucleoli. As regards the special stains used in the FAB classification, ALL lymphoblasts generally show positive ...

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