EHA Library - The official digital education library of European Hematology Association (EHA)

Follicular lymphoma (FL) may evolve to diffuse large B-cell lymphoma (DLBCL) and interactions between neoplastic cells and immune tumour microenvironment have been involved in this process. However, the potential value of the peripheral blood study to identify FL patients at high risk of progression is less known.

The study (performed between September 2012 and January 2017) included 52 patients (50% female) with a median age of 70.5 years (71% >60 years). Patients were newly diagnosed with in situ FL (n=1), Grade 1,2 FL (n=12), Grade 3 FL (n=11), and DLBCL not otherwise specified (n=28). In situ FL and Grade 1,2 FL were grouped as low-grade FL. Most patients with FL (11/13 low-grade FL and 8/11 Grade 3 FL) had clinical stages III/IV. Patients with primary or secondary immunodeficiency and those who had already received corticosteroids or chemotherapy were excluded from this study. A whole blood sample was studied at diagnosis of lymphoma and prior to the start of therapy, using multicolour flow cytometry immunophenotyping and a standard stain-lyse-wash protocol. A single monoclonal antibody panel including reagents against CD19, CD20, CD22, kappa, lambda, CD3, CD4, CD8, CD56 and CD45 was used, and a minimum of 300,000 events were acquired on the flow cytometer. Results were expressed as the absolute number/ml of monocytes, lymphocytes, T cells, CD4, CD8 and NK cells. Polyclonal and monoclonal B lymphocytes were also identified.

No difference in the distribution by sex or age was found between patients with FL and DLBCL. A low cell count in at least, one lymphocyte population was detected in 35/52 patients (67.3%); 100% of cases had a low number of polyclonal B cells (<100/ml).Comparison of low-grade FL, grade 3 FL and DLBCL did not show any statistically significant difference regarding monocytes, CD4, CD8 and total T cells. Low-grade FL and DLBCL showed the highest number of differences, involving lymphocytes (2571±2439 versus 1495±671, p=0.001), NK cells (381±312 versus 204±167, p=0.03), the CD4:CD8 ratio (1.54±0.49 versus 2.06±1.44, p=0.002), and circulating monoclonal B cells, for both percentage (15.2±23.23 versus 1.94±5.23, p<0.001) and absolute number (869±1758 versus 18.75±46.47, p<0.001). Grade 3 FL and DLBCL also showed a different CD4:CD8 ratio (1.16±0.45 versus 2.06±1.44, p=0.001), with a trend toward significance regarding CD4 T cells (413±184 versus 685±457, p=0.077). Grade 3 FL had a lower number of polyclonal B cells as compared to DLBCL (66±41 versus 105±102, p=0.048). The peripheral expression of monoclonal B cells was higher in low-grade FL than in grade 3 FL, in both percentage (15.2±23.23 versus 4.58±8.48, p=0.008) and number (869±1758 versus 43.36±69.91, p=0.002) of monoclonal B cells. The number of lymphocyte subpopulations (≤1 versus ≥2) with low-cell counts was higher in grade 3 FL than in low-grade FL (p=0.03).

The peripheral lymphocyte profile in patients with FL and DLBCL is heterogeneous, but B-lymphopenia and CD4:CD8 ratio deviations are frequent findings. Regardless of clinical stage, low-grade FL had more circulating lymphoma cells and preserved lymphocyte populations than grade 3 FL. Further studies are warranted to confirm these exploratory findings and determine their clinical implications.