Cell Morphology

Cell Morphology

  • HEME 1304

  • February 2025

Red Blood Cell Morphology

  • Hemoglobin

  • Size Variations

    • Normal distribution includes variations such as microcytes, macrocytes, and spherocytes.

  • Shape Variations

    • Abnormal shapes include:

      • Target cell

      • Acanthocyte

      • Helmet cell

      • Stomatocyte

      • Tear drop

      • Schistocyte (fragmented cell)

      • Spherocyte

  • Inclusions and Aggravating Factors

    • Pappenheimer bodies

    • Agglutination (siderotic granules)

Red Blood Cell (RBC) Characteristics

  • Structure

    • Discocyte shape, biconcave disc

    • Lacks nucleus and organelles

    • Average size is 7-8 μm with a volume of 90 fL

  • Function

    • Transports oxygen and removes carbon dioxide

    • Pliable membrane consisting of lipids and proteins

Assessment of RBC Morphology

  • Requires a well-stained smear with even RBC distribution.

  • Anisocytosis Assessment

    • Size variation; assisted by RBC indices and RDW (Red Cell Distribution Width)

    • Evaluation of 10 OIF (Oil Immersion Field).

    • Qualitative (few/moderate) or quantitative (1+ to 4+) descriptors used for reporting.

Grading Scale for RBC Morphology

  • Normal: 5% variation

  • Slight: 5-10% (1+)

  • Moderate: 10-25% (2+)

  • Severe: 25-50% (3+)

  • Extreme: >75% (4+)

Variations in RBC Distribution

  • Normal Distribution

    • Good interpretative areas in slide; overlapping indicates poor descriptions.

    • Thin areas of the slide should represent about 1/3 of the entire film.

Abnormal Distribution

  • Agglutination

    • Clustering due to antigen/antibody reactions

    • Commonly seen in conditions like cold hemagglutinin disease

    • Saline won't disperse agglutination—warming to 37 degrees is sometimes necessary.

RBC Indices with Agglutination

  • MCHC (Mean Corpuscular Hemoglobin Concentration) and MCV (Mean Corpuscular Volume) can appear falsely elevated in agglutination.

Rouleaux Formation

  • Appearance as stacks of coins due to increased globulins or fibrinogen.

  • Saline Dilution

    • Can help disperse rouleaux; significant piles may indicate high ESR (Erythrocyte Sedimentation Rate).

Identification of Rouleaux

  • Common Conditions

    • Seen in hyperproteinemic states, multiple myeloma, and chronic inflammatory disorders.

    • Artefactual when observed in thick slide areas—confirm in thinner areas.

Variations in RBC Size

  • Definition: Significant variance in size (anisocytosis).

  • Identification: RDW critical in assessing anemias.

  • Size Classifications:

    • Microcytes: < 6 μm

    • Macrocytes: > 9 μm

Reporting Anisocytosis

  • Microcytosis and macrocytosis should align with RBC indices.

  • Can report as a dimorphic population when applicable.

Normocytes and Macrocytes

  • Normocytes:

    • MCV of 80-100 fL, inclusive of all cells measuring 7-8 μm.

    • High RDW with normal MCV could suggest post-transfusion recovery.

  • Macrocytes:

    • Defined as >9 μm or MCV >100 fL.

    • Commonly linked to impaired DNA synthesis—important in megaloblastic anemias.

Macrocyte Morphology

  • Involves various conditions including liver disease and megaloblastic anemia.

Microcytes

  • Size < 7 μm or MCV < 80 fL signals microcytic anemia.

  • Associated factors include iron deficiency, thalassemia, and chronic disease states.

Hypochromia in RBCs

  • Defined as having a central pallor exceeding 3 μm.

  • Indicates less than normal hemoglobin content.

Hyperchromia Characteristics

  • Hyperchromic RBCs feature reduced surface-to-volume ratios.

  • True concentration diagnosed when MCHC exceeds 360.

Polychromasia Attributes

  • Appears as larger, diffusely basophilic cells, implied reticulocytes.

Variations in Shape (Poikilocytosis)

  • Poikilocytosis refers to the alteration in RBC morphology (i.e., tear drops, sickles).

Target Cells (Codocytes)

  • Exhibits increased surface membrane area, commonly linked to liver diseases and hemoglobinopathies.

Spherocytes

  • Characterized by no central pallor, often seen in autoimmune hemolytic anemia and related disorders.

Stomatocytes

  • Identified by a slit-like central pallor, may indicate membrane defects.

Ovalocyte and Elliptocyte Distinctions

  • Ovalocytes: egg-shaped, frequently noted in megaloblastic anemia.

  • Elliptocytes: often pencil-shaped; linked to hereditary conditions.

Sickle Cells (Drepanocytes)

  • Crescent-shaped with rigid nature, typically in patients with abnormal hemoglobin S.

Fragmented Cells (Schistocytes)

  • Result from membrane trauma and are indicators of severe hematological conditions.

Helmet/Bite Cells

  • Result of RBCs getting stuck on fibrin strands, experiencing morphological changes from large inclusions.

Morphology of Fragmented Cells

  • Includes schistocytes and conditions influencing their shapes and characteristics.

Echinocytes (Burr Cells)

  • Frequently artifacts showing 10-30 spicules; associated with dehydration and uremic states.

Acanthocytes (Thorn Cells)

  • Notable for unevenly spaced projections; associated with numerous disorders including liver disease.

Teardrop Cells (Dacrocytes)

  • Pinched cells linked to myelofibrosis and associated conditions.

Red Cell Inclusions

  • Howell Jolly Bodies: remnants of DNA, common in splenic dysfunctions.

  • Basophilic Stippling: indicates biosynthesis issues, often seen across various types of anemia.

Pappenheimer Bodies (Siderotic Granules)

  • Irregular inclusions in RBCs indicating iron presence, notable in iron overload disorders.

Heinz Bodies

  • Resultant from hemoglobin denaturation; not visible via typical stains.

Cabot Rings

  • Retained microtubule fragments likely indicative of megaloblastic anemia.

Hemoglobin Crystals (CC and SC)

  • Crystallizations indicate specific hemoglobinopathies and notable pathological states.

Protozoan Inclusions

  • Plasmodium species cited, indicating malaria; significant for differential diagnosis in infectious diseases.