16 Target Cells (Codocytes)
Michelle To and Valentin Villatoro
Images show peripheral blood smears with numerous target cells present (examples are indicated by arrows). From MLS Collection, University of Alberta.
Image 1: 100x oil immersion. https://doi.org/10.7939/R3R49GR23
Image 2: 40x magnification. https://doi.org/10.7939/R3NG4H71X
Image 3. 60x oil immersion. https://doi.org/10.7939/R3R78644B
Target cells adopt a “bullseye” morphology where hemoglobin is concentrated in the center and on the periphery with a colourless zone in between the two areas. Other target cells may also look folded or bell shaped.1-3
Note: The target cell membrane is thinner than normal cells.1,4
Liver Disease: membrane cholesterol concentration is reduced, decreasing the tensile strength of the membrane, resulting in target cell formation.2,3,5
Artifact: Target cell formation occurs when blood smears are made when humidity is high.1
Hemoglobinopathies: There is a uneven distribution of hemoglobin within the cell, and an increased surface area to volume ratio.1
Note: Target cells have an increased surface area to volume ratio and decreased osmotic fragility.1,3
Associated Disease/Clinical States:1,2,5
Hemoglobinopathies (Hemoglobin C Disease, Sickle cell Disease, Thalassemia, etc.)
Iron deficiency anemia
Obstructive Liver disease
1. Landis-Piwowar K, Landis J, Keila P. The complete blood count and peripheral blood smear evaluation. In: Clinical laboratory hematology. 3rd ed. New Jersey: Pearson; 2015. p. 154-77.
2. Rodak BF, Carr JH. Variations in shape and distribution of erythrocytes. In: Clinical hematology atlas. 5th ed. St. Louis, Missouri: Elsevier Inc.; 2017. p. 93-106.
3. Jones KW. Evaluation of cell morphology and introduction to platelet and white blood cell morphology. In: Clinical hematology and fundamentals of hemostasis. 5th ed. Philadelphia: F.A. Davis Company; 2009. p. 93-116.
4. Bain BJ. Morphology of blood cells. In: Blood cells: a practical guide [Internet]. 5th ed. Chichester, UK: John Wiley & Sons, Ltd; 2015 [cited 2018 Jul 10]: 67-185. Available from: http://doi.wiley.com/10.1002/9781118817322
5. Turgeon ML. Erythrocyte morphology and inclusions. In: Clinical hematology: theory and procedures. 4th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 1999. p. 99-111.