Reactive Lymphocyte vs Monocyte in Peripheral Blood Smears : Points of differentiation

  1. Size can go upto 30 microns, which is much larger than a normal monocyte
  2. Nucleus may show areas of light staining which resemble nucleoli
  3. There will not be any vacuoles in the cytoplasm
  4. The cytoplasm will form contours with nearby RBC’s , and the edges will stain darker blue, than the rest of the cytoplasm


  1. The monocyte is larger than all the other cells, around 15–18 microns.
  2. It has a more convoluted nucleus
  3. The cytoplasm is more pale than that of a reactive lymphocyte
  4. The cytoplasm should show vacuoles, with debris.
  5. The cytoplasm does not form contours around neighbouring RBC’s.

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Bhargav Raut

Bhargav Raut

Post-Graduate in Clinical Pathology, Lab Director - Pathofast, Computer Vision Enthusiast, Founder