Morphologic and Phenotypic Features of Concurrent Clonal T-Cell Large Granular Lymphocytic Expansion and Myelodysplastic Syndrome

Clinical and pathologic data from patients with a diagnosis of MDS and flow cytometry performed on the peripheral blood between 1/2005 and 12/2009 were reviewed. The concurrent bone marrow biopsies from each patient at the time of flow cytometric analysis were reviewed by two hematopathologists. Bone marrow cellularity, lineage hypoplasia (M:E >5: 1 or <1:2) were documented. Peripheral lymphocyte count and CD3+/CD57+ and CD8+/CD57+ populations by flow cytometry were calculated and T cell gene receptor (TCR) rearrangements were correlated.

We performed LGL flow cytometry panel on 76 MDS patients (high grade MDS, n=23; low grade, n=54), as well as TCR gene rearrangements, and identified clonal T-LGL cells in peripheral blood of 37 patients (48.7%), including 15 high grade MDS (40.5%, RAEB-I and RAEB-II), and 22 low grade MDS (59.4%), including RCMD(13), RA(1), RS(1), RCMD-RA(1), RCMD-RS (2), 5q- MDS(1), and MDS unclassifiable(3). The immunophenotype of the T-LGL cells was typically CD3+/CD57+/CD7 dim+/CD5 dim+/CD8+ with variable CD11b,CD11c, CD16, CD56 and HLA-DR. A frequent variant in these MDS patients was CD11b-,CD11c -, CD16+/−, CD56+/−, HLA-DR- and CD62L+.The TCRβ or/and TCRγ gene rearrangements were positive in 35 of the 38 cases (92.1%). The peripheral blood lymphocyte counts were 300–3820 cells/μL (1199±799 cells/μL); the CD3+/CD8+/CD57+ T-LGL cell counts were 30–624 cells/μL (229±154 cells/μL). In comparison, the remaining 39 patients with non-clonal T-LGL included 11 high grade MDS cases, and 28 low grade MDS cases. The peripheral blood lymphocyte counts were 308–2210 cells/μL (1030±461 cells/μL). CD3+/CD57+ cells were 1–425 cells/μL (105±98 cells/μL). There was no identifiable phenotypic features suggestive of clonal T-LGL cells such as dim CD5 and/or dim CD7 with aforementioned aberrant expressions on T-cells, although 7 of the 39 cases had TCRβ or/and TCRγ gene rearrangements. Thirty healthy donors were included for controls with absolute lymphocyte counts of 2136±661 cells/μL and baseline CD3+/CD57+ cells of 162±109 cells/μL. All showed no clonal LGL phenotype and negative TCR gene rearrangements.

Since the presence of T-LGL cells may impair bone marrow hematopoiesis, we examined if there are bone marrow status differences between these two groups. All the bone marrows were obtained at diagnosis or not on chemotherapy. The bone marrow cellularity of the MDS patients with clonal T-LGL ranged from <3% to almost 100%, averaging 56%, with 8 cases with dramatic hypocellularity (<3%-20%), while the bone marrow cellularity of the MDS patients without clonal T-LGL ranged from 20% to 90%, averaging 62%, with only 2 cases with mild hypocellularity (20% in 73- and 65-year-old). In addition, among MDS patients with clonal T-LGL cells, 14 of 37 (37.8%; 5 high grade, and 9 low grade) bone marrows had certain lineage hypoplasia, including 3 cases of trilineal hypoplasia, 9 cases of erythroid hypoplasia, and 2 cases of myeloid hypoplasia. In contrast, among 39 MDS patients without T-LGL, there were only 1 bone marrow with trilineal hypoplasia and 3 others with erythroid hypoplasia (10.2%). The difference between the two groups was statistically significant (p=0.004, chi square test).

In conclusion, our studies indicate that clonal T-LGL cells expansion is a fairly common finding in high grade as well as low grade MDS. The clonal T-LGL cells have more than one variant immunophenotypes and are typically positive for TCR gene rearrangements. Additionally, we observed that the clonal LGL cells present in MDS bone marrows could be associated with lineage hypoplasia, which, in this respect, might impact clinical treatment.

No relevant conflicts of interest to declare.