H. H. Rashidi, MD
J. C. Nguyen, MD
HematologyOutlines.com

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Primary Hematopoietic and Lymphoid Tissue ›› Bone Marrow ›› Lymphoid ›› NK Cells ›› Normal

NK Cell

NK Cell
NK Cell
NK Cell

›Microscopic Features:

  • Slightly larger than a mature RBC High nuclear to cytoplasmic ratio but with a Round mature Nucleus (clumped chromatin) Nucleoli are absent Cytoplasm may have some granules

›Normal % blood-PB, marrow-BM, lymphoid tissue-LN:

  • PB: Rare scattered (Note that lymphocytes in general are the 2nd most common WBCs in blood. Majority are T-cells, followed by scattered B-cells and rare scattered NK-cells)
  • BM: Rare scattered
  • LN: Rare scattered

›May Resemble:

  • Mature T-cell (can't distinguish it from mature T-cell or B-cells based on morphology)
  • Mature B-cell (can't distinguish it from mature T-cell or B-cells based on morphology)
  • Reactive lymphocyte
  • Monocyte

›Differential Diagnoses:

If increased in blood, Lymph node or bone marrow:
Infection
Neoplastic (NK cell leukemia and lymphoma)

›Classic Immunophenotype:

  • surface CD3- (as opposed to T-cells which are +)
  • CD2+ (similar to T-cells)
  • CD5- (as opposed to T-cells which are +)
  • CD7+ (similar to T-cells)
  • TCR- (as opposed to T-cells which are +)

›Cartoon Image:

NK Cell cartoon
Click and dragRed blood cell for scalefor direct comparison

›Misc:

Morphologically you cannot distinguish NK cells from mature T-cells or mature B-cells