T-Cell Large Granular Leukemia (LGL)

T-cell large granular lymphocyte leukemia (T-LGL) exhibits a unexplained, chronic (> 6 months) elevation in large granularlymphocytes (LGLs) in the peripheral blood. It is also known by : Proliferation of large granular lymphocytes (LGLs), LGL leukemia, Tγ-lymphoproliferative disorder, T-cell chronic lymphocytic leukemia.

Sample Cases

Click here for instructions on how to download the free FCS Express Reader to view and manipulate the sample cases.

Case Name (click on case name to open)	Comments	Size
LGL1	LGL	5.44 MB
case 29	variant T LGL   This case was kindly provided by the ASCP Press. It is part of Flow Cytometry in Clinical Diagnosis by John Carey, Phil McCoy and David Keren.	1.37 MB
case 17	LGL   This case was kindly provided by the ASCP Press. It is part of Flow Cytometry in Clinical Diagnosis by John Carey, Phil McCoy and David Keren	1037 kB

Epidemiology

T-LGL is a rare form of leukemia, which comprises 2-3% of all cases of small lymphocytic leukemias.

Possible causes

Unknown.

Morphology

In periperal blood the neoplastic lymphocytes are large in size with azurophilic granules that contains proteins involved in cell lysis such as perforin and granzyme B. Bone marrow involvement is often present, but to a variable extent. The lymphocytic infiltrate is usually interstitial and/or intrasinusoidal, but a nodular pattern can rarely occur. The leukemic cells of T-LGL can be found in peripheral blood, bone marrow, spleen, and liver. Nodal involvement is rare.

Example morphology of T-LGL lymphocytes from Wright-stained cytospin of ficoled blood lymphs. These cells characteristically have abundant cytoplasm and azurophillic granules.

Immunophenotyping

T-LGL presents as a predominance of lymphocytes. These cells will display bright CD45 and low SSC and fall into the same region as normal (benign) lymphocytes.  

LGL lymphocytes (red) displayed on a CD45 vs SSC gating dot plot.

In the table below (3) are immunophenotypic markers that are useful in identifying and classifying LGL. The table is stratified into T-LGL and NK-LGL as they display different phenotypes.  

Marker	T-LGL (%)	NK-LGL (%)
CD2+	100	100
CD3+	100	0
CD5+	80	0
CD7+	83	100
All pan T cell Ags +	63	0
CD4+	2	0
CD8+	85	21
CD4+/CD8+	10	0
CD4-/CD8-	3	79
TCR ab+	80	7
TCR gd+	20	0
TCR -	0	93
CD11c+	44	71
CD16+	32	71
CD56+	32	71
CD57+	95	64

Below are examples of selected dot plots from a case of LGL.                     

The pan T cell markers CD2, CD7 and CD3 are generally expressed, with a CD8 phenotype. CD4 is usually absent or minimal.	LGL display a predominant CD8 phenotype. The pan T cell markers is usually expressed, but many times one of the T cell markers is aberrantly negative or underexpressed.	CD7  is usually expressed on LGL. The NK markers CD56 and CD16 are usually expressed on about 1/3 of these cases.