Chronic lymphoproliferative disorder of NK cells pathophysiology

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Pathophysiology

Clinical features

This pathology affects primarily the bone marrow. Generally patients are asymptomatic, although some present with diverse cytopenias, mainly anemia and neutropenia. Less frequently, patients may present with hepatomegaly, splenomegaly and cutaneous lessions.

Chronic lymphoproliferative disorder of NK cells have been associated with other hematological tumors, vasculitis, splenectomy, neuropathy and autoimmune diseases.

Morphology

Circulating NK cells tend to be intermediate size with a round nucleus and condensed chromatin, with basofilix cytoplasm and azurophilic granules. The bone marrow biopsy, instead, show intrasinusoidal and interstitial infiltration of small cells with small and irregular nucleus and pale cytoplasm.

Immunophenotype

  • Surface CD3 is negative, while cytoplasmic CD3 tends to be positive.
  • CD16 positive
  • Weak expression of CD56
  • Cytotoxic markers: TIA-1, granzyme B and granzyme M positive.
  • Diminished expression of CD2, CD7 and CD57.
  • Aberrant expression of CD5 and CD8.
  • Diminished CD161 expression.