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Question 5

The following figure presents blood smear of a woman with a history of pancytopenia and splenomegaly for the last six months.
Approximately 35% of her lymphocytes were granular and expressed CD16 and CD56 but were negative for CD3.

These lymphocytes represent:
a. Natural killer (NK) cells
b. Cytotoxic T cells
c. Helper T cells
d. Prolymphocytes

The answer is: a

Large granular lymphoproliferative disorder, also referred to as large granular lymphocytic leukemia(LGLL) and T-gamma lymphoproliferative disorder, is a rare chronic lymphoproliferative disorder characterized by clonal proliferation of large granular lymphocytes.
The large granular lymphocytes (LGL) are approximately twice the size of erythrocytes, have moderate to abundant cytoplasm with multiple azurophilic granules, round nuclei with condensed chromatin, and inconspicuous nucleoli.
The criteria for the diagnosis of LGLL are not well-established. The currently proposed criteria include persistent lymphocytosis (at least six months after initial presentation), increased proportion (>25%) and/or absolute numbers (>1X106/ml) of morphologically-defined LGLs, and/or phenotypically-defined NK-associated (CD16, CD56, CD57) cells.317


CD3-positive variant (T-LGLL) which is considered a T cell, usually of suppressor/cytotoxic type, and is associated with T-cell receptor gene rearrangement. This is the predominant form accounting for 55% to 80% of cases.

CD3-negative variant (NK-LGLL) which is considered a true NK cell disorder and is not associated with T-cell receptor gene rearrangement.