MH 034bhr Bone Marrow Smear

Basophilic Myelocyte

Basophils develop from the multipotential myeloid stem cell (CFU-GEMM) which differentiates into basophil progenitor cells (CFU-Baso).

Basophilic myeloblasts are produced from progenitor cells (CFU-Baso) under the influence of cytokines. The basophilic myeloblast matures into a basophilic promyelocyte. These cells cannot be distinguished from cells at the same stage in other granulocyte lineages.

Basophilic myelocyte is the first recognizable precursor of basophils.

• Large cells (18 to 20 µm diameter)
• Round, oval, or indented nucleus (50% of cell) with a coarser, granular pattern of chromatin
• Cytoplasm is pale blue
• Very basophilic, specific granules begin to accumulate
• Azurophilic granules
• Last cell type capable of mitosis

It is difficult to find developing basophils because they account for less than 0.5% of granulocytes.

Example:

• Basophilic myelocyte (60x) [+]

Basophilic Metamyelocyte

The basophilic myelocyte matures into a basophilic 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
• Many very basophilic, specific granules
• Few azurophilic granules
• No longer capable of mitosis

Example:

• Basophilic Metamyelocyte (60x) [+]

Band Basophil

The basophilic metamyelocyte matures into a band basophil.

• 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
• Many very basophilic, specific granules
• Few azurophilic granules
• No longer capable of mitosis

No band basophil is found on this slide.

Basophil

The band basophil develops into a mature basophil. Basophils mediate inflammatory responses.

• Rare white blood cells (<1%)
• Smaller cells (10 to 12 µm diameter)
• Nucleus bilobed or S-shaped
• Cytoplasm is a pale blue-pink
• Many very basophilic, specific granules
• Few azurophilic granules
• No longer capable of mitosis

Examples:

• Basophil #1 (60x) [+]

• Basophil #2 (60x) [+]

• Basophil #3 (60x) [+]