Summary

This case is from a 28-year-old male patient with non-Hodgkins B-cell follicular lymphoma (Grade 3). Before the WHO/REAL classification, follicular lymphomas were subdivided into 3 groups according to the ratio of small-cleaved to large cells (this system implied different disease subtypes). In the new classification, all follicular lymphomas are classified by the grade of the disease, which varies from case to case. The Berard cell-counting method is both clinically relevant and reproducible for separating follicular lymphomas into 3 grades. It enumerates the number of large centroblasts (large cells) per high-power field (hpf): Grade 1: 0-5 centroblasts/hpf, Grade 2: 6-15 centroblasts/hpf, Grade 3: >15 centroblasts/hpf. Translocation t(14;18) (q32;q21) detected by cytogenetic techniques is found in 80-90% of follicular lymphomas. The translocation can be identified by metaphase cytogenetics and interface Fluorescence in situ Hybridization (FISH). In this sample there is only one predominant population identified corresponding to lymphocytes. This case was positive for CD45 and FMC7, co-expression of CD10 CD19, and a small population showed CD23 positivity. There was a polyclonal population of kappa and lambda positive light chains. However an overlay of the kappa and lambda light chains shows that there are dim lambda events not present in the kappa staining as shown in scatterplot 7. Also the kappa to lambda ratio is usually in the range of 1-1.5 to 1. In this case, the ratio is reversed and is 0.38 to 1. This case did not demonstrate the t(14;18) translocation, it was classified as a follicular lymphoma by both histology and flow cytometry.