Red Cell Staining (Color)

Central pallor

  • Introduction
    • A normal red blood cell has a biconcave disk shape. Because the center is much thinner than the periphery, it creates the illusion of a Hb-free center on a peripheral smear. The area of pallor in its center (about 1/3 of the diameter of the cell) when viewed under the light microscope. 

Cells | Free Full-Text | Modeling of Red Blood Cells in Capillary Flow  Using Fluid–Structure Interaction and Gas Diffusion

      • The area of central pallor may be:
        • Normal (normochromia)
        • Increased (hypochromia)
        • Decreased (hyperchromia)
      • The color can be evaluated by the mean corpuscular hemoglobin concentration (MCHC). 
  • Hypochromia
    • Hypochromic red blood cells have less color (> 1/3 central pallor) than normal when examined under a microscope. 
    • The decrease in redness is due to a disproportionate reduction of red cell hemoglobin (the pigment that imparts the red color) in proportion to the volume of the cell. 
    • Hypochromia correlates with a lower than normal MCHC. 
    • The MCHC, in turn, is helpful in distinguishing between causes of microcytic anemia. 
    • Differential diagnosis of hypochromia includes:
      • Iron deficiency 
      • Thalassemia intermedia/major
      • Anemia of inflammation
      • Sideroblastic anemia
  • Hyperchromia
    • Refers to an increase in the intensity of red blood cell color.
    • The area of central pallor is decreased or gone.
    • Correlates with a higher than normal MCHC. 
    • Hyperchromic cells may be:
      • Spherocytes
      • Microspherocytes
      • Sickle cells
      • Spur cells
      • Schistocytes
      • HbC cells
    • Differential diagnosis includes:
      • Spurious
      • Autoimmune hemolytic anemia
      • Hereditary spherocytosis
      • HbC
      • Spur cell anemia
      • Microangiopathic hemolytic anemia



  • Immature non-nucleated red cells with a blue hue in their cytoplasm.
  • The blue may be barely visible or may be marked.
  • Polychromatic red cells are typically larger than normal red cells.
  • They tend to lack central pallor.
  • When stained with supravital dyes the remaining mRNA and ribosomes give the red cells a “reticular” mesh-like network, hence the name “reticulocyte”.
  • Of note, white the vast majority of polychromatophilic cells are reticulocytes (as defined by the presence of reticulum on a reticulocyte stain), not all reticulocytes are recognized as polychromatophils on the Wright-Giemsa stain.

Peripheral smear from a 25-year-old woman with GI bleed shows multiple polychromatophilic red cells (polychromatophilia) 100x (oil).

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