Lab

Bone Marrow Exam

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Bone Marrow Exam, Bone Marrow, Prolymphocyte, Erythroblast, Granuloblast, Megakaryocyte, Megalokaryocyte

  • Physiology
  1. Bone Marrow produces lymphocytic progenitor cells
    1. Lymphoblasts form in marrow, divide to Prolymphocytes
    2. Prolymphocytes develop into 2 separate cell lines
      1. B-Lymphocytes develop in Bone Marrow
      2. T-Lymphocytes develop in Thymus
  2. Bone Marrow produces three stem cell myeloid lines
    1. Erythroblasts (Initial cell known as Proerythroblast)
      1. Develop into erythrocytes (Erythropoiesis)
    2. Myeloblasts (Granuloblasts)
      1. Represent 75% of nucleated cells in marrow
      2. Develop into Promyelocyte and then Granulocyte
      3. Characteristics
        1. Evenly distributed fine chromatin
        2. Multiple nucleoli
        3. Basophilic cytoplasm (non-granular)
    3. Megakaryocyte (Megalokaryocyte)
      1. Giant cell with multi-lobulated nucleus in marrow
      2. Releases mature blood platelets from cytoplasm
  • Background
  1. Minimum of 500 cells must be counted
  2. Sample staining
    1. Wright Stain or
    2. May-Grunwald-Giemsa Stain
  • Normal Bone Marrow Examination Findings
  1. Fat to Cell Ratio
    1. Child under age 10 years: 10% fat to 90% cells
    2. Adult: 30% - 70% fat to 70% - 30% cells
  2. Myeloid to Erythroid ratio: 3 to 1 ratio
  3. Erythroid Cells: 18 to 39% of marrow nucleated cells
  4. Megakaryocytes: 0.5 to 2% of nucleated cells in marrow
  5. Lymphocytes: 11 to 23% of nucleated cells in marrow
    1. T-Lymphocyte to B-Lymphocyte ratio: 3 to 1
  6. Plasma Cells: 0.4 to 3.9% of nucleated cells in marrow
  7. Myeloid Cells: 60-75% of nucleated cells in marrow
    1. Neutrophilic series: 49 to 65%
    2. Eosinophilic series: 1.2 to 5.3%
    3. Basophilic series and mast cells: <0.2%
  • References
  1. Lee (1999) Wintrobe's Hematology, Lippincott, p. 23-25