Herein we reported a case of follicular lymphoma with 50.26% clonal malignant lymphocytes and 50% tumor cells positive for the immunoglobulin heavy chain gene and B-cell lymphoma 2 gene (IGH-BCL2). To determine whether endothelial cells (ECs) within the tumor share the feature of advanced malignancy, we isolated and purified the ECs from the tumor by using the immunomagnetic beads conjugated with a monoclonal antibody against CD34, a surface marker of ECs. Thereafter, we identified ECs according to their morphology and found that ECs presented consistently flat and elongated appearance with a lot of Weibel-Palade bodies in the cytoplasm. Results of flow cytometry confirmed that ECs isolated from the follicular lymphoma expressed high level of both vWF and CD34 and the purity of the ECs fraction was more than 90%. Additionally, we used FISH to check chromosomal aberration in the purified ECs and found that some of the ECs had only one fusion signal for the green IGH probe and the red BCL2 probe in contrast to typical t(14;18)(q32;q21) translocation with two fusion signals. This phenomenon was also observed in the tumor cells. It might be a different breakpoint of IGH in this case, which induced the loss of the fusion signal, indicating t(14;18)(q32;q21) translocation. The positive cells accounted for 18% of the isolated ECs from the tumor, indicating that a proportion of ECs from follicular lymphoma had the same chromosome aberration as the neoplastic cells.