Changes in the tumor microenvironment associated with transformation in follicular lymphoma.

8538 Background: Follicular lymphoma (FL) is a heterogeneous disease with a variable prognosis. Transformation to an aggressive lymphoma is associated with a poor prognosis. Previous studies have identified tumor microenvironment cells such as CD68+ macrophages, PD-1+ and FOXP3+ cells as prognostic in FL. However, results have been conflicting and infrequently address the risk of transformation. In this study we analyzed various components of the microenvironment and their association with transformation. Methods: Patients with FL that later transformed were identified through Mayo Clinic lymphoma database. Tissue specimens at diagnosis were stained with CD68, CD11c, CD21, CXCL13, FOXP3, PD-1 and CD14 and characterized by pattern of location and semi-quantitative cell content. Time to transformation (TTT) and overall survival (OS) were assessed by Kaplan-Meir analysis. Significant variables were further analyzed by cox proportional hazards model. Results: 58 patients were included with a median TTT of 4.7...