MH 034bhr Bone Marrow Smear

Myeloblast

Granulocytes develop from the multipotential myeloid stem cell (CFU-GEMM) which differentiates into lineage-specific progenitor cells.

• Neutrophil progenitor cells (CFU-G)
• Eosinophil progenitor cells (CFU-Eo)
• Basophil progenitor cells (CFU-Baso)

Myeloblasts are produced from these progenitor cells under the influence of cytokines. Myeloblasts are the first recognizable precursor of granulocytes.

• Large cells (12 to 18 µm diameter)
• Large, round or oval nucleus (85 to 90% of cell) of euchromatin (fine, granular pattern)
• Small amount of cytoplasm that is pink-blue to light blue
• No granules
• Capable of mitosis

Myeloblasts of specific lineages cannot be distinguished from each other. They are rare cells that are difficult distinguish from other types of cells (for example, large lymphocytes).

• Myeloblast 1(60x)[ + ]

• Myeloblast 2(60x)[ + ]

• Myeloblast 3(60x)[ + ]

Promyelocyte

The myeloblast matures into a promyelocyte.

• Larger cells (16 to 22 µm diameter)
• Round, oval or indented nucleus (65 to 80% of cell) with more condensed chromatin (a coarser, granular pattern)
• Increased amount of blue cytoplasm
• Azurophilic granules are only produced in this stage
• Capable of mitosis

Examples:

• Promyelocyte 1(60x)[ + ] - just beginning production of azurophilic granules

• Promyelocyte 2(60x)[ + ] - just beginning production of azurophilic granules

• Promyelocyte 3(60x)[ + ] - many azurophilic granules

• Promyelocyte 4(60x)[ + ] - many azurophilic granules

Promyelocytes of different granulocyte lineages cannot be distinguished from each other.

Neutrophilic Myelocyte

The neutrophilic promyelocyte matures into a neutrophilic myelocyte.

This is the first stage in which precursors of the different granulocyte lineages can be distinguished from each other because of the presence of specific granules.

• Larger cells (18 to 20 µm diameter)
• Round, oval or indented nucleus (50% of cell) with a coarser, granular pattern of chromatin
• Cytoplasm is lighter blue
• Specific granules appear for the first time
• Fewer azurophilic granules
• Last cell type capable of mitosis

Examples:

• Neutrophilic Myelocyte 1(60x)[ + ]

• Neutrophilic Myelocyte 2(60x)[ + ]

• Neutrophilic Myelocytes 3(60x)[ + ]

• Neutrophilic Myelocyte 4(60x)[ + ]

Neutrophilic Metamyelocyte

The neutrophilic myelocyte matures into a neutrophilic metamyelocyte.

• Smaller cells (12 to 17 µm diameter)
• Nucleus is dented, kidney shaped (50% of cell) of mostly heterochromatin
• Cytoplasm ranges from blue-gray to pink-gray
• Pink-salmon specific granules
• Few azurophilic granules
• No longer capable of mitosis

Examples:

• Neutrophilic Metamyelocyte 1(60x)[ + ]

• Neutrophilic Metamyelocyte 2(60x)[ + ]

• Neutrophilic Metamyelocyte 3(60x)[ + ]

• Neutrophilic Metamyelocyte 4(60x)[ + ]

Band Neutrophil

The neutrophilic metamyelocyte matures into a band neutrophil.

• Smaller cells (10 to 12 µm diameter)
• Nucleus is elongated and often has a horseshoe-like ("U") appearance that contains heterochromatin
• Cytoplasm is a pale blue-pink
• Pink-salmon specific granules
• Few azurophilic granules
• No longer capable of mitosis

Examples:

• Band Neutrophil 1(60x)[ + ]

• Band Neutrophil 2(60x)[ + ]

• Band Neutrophils 3(60x)[ + ]

• Band Neutrophil 4(60x)[ + ]

Neutrophil

The band neutrophil develops into a mature neutrophil. Neutrophils phagocytose and destroy bacteria.

• 10 to 15 µm diameter
• Segmented nucleus with three to five lobes
• Cytoplasm is a pale blue-pink
• Specific granules are pink-salmon
• Few azurophilic granules
• No longer capable of mitosis

Examples:

• Neutrophil 1(60x)[ + ]

• Neutrophil 2(60x)[ + ]

• Neutrophils 3(60x)[ + ]

• Neutrophils 4(60x)[ + ]

Mature neutrophils are released from bone marrow into the peripheral circulation. They circulate in blood for 8 to 16 hrs. Their tissue life span is only 1 to 2 days.