Appearance of Mononuclear Cells

Differentiating Monocytes from Large Lymphocytes



  • At times it can be very difficult to differentiate monocytes from large lymphocytes.
  • Monocytes may be mistaken for large lymphs when their cytoplasm stains too lightly, when the characteristic granules are indistinct, or when the nucleus is rounded or only slightly indented.
  • Sometimes a cell will have the nucleus of a lymphocyte and the cytoplasm of a monocyte, or some other confusing combination of characteristics.
  • In order to properly identify the cell, it is necessary to weigh all of the characteristics together to determine which cell type it most resembles.
  • Even then it is occasionally necessary to judge the cell on the basis of the company it keeps.
  • For instance, if there are many monocytes, but few large lymphocytes around, the confusing cell is probably a mono.

    • Review for ASCP Boards or test your clinical laboratory science knowledge with the FREE LabCE.com Quiz Game.

    Normal Peripheral Blood Cells course details »

    Learn more about medical technologist continuing education for MTs, MLTs, and other lab personnel »

    Get information on laboratory safety training for clinical and medical laboratories »