Tumor Microenvironment and Microvascular Density in Follicular Lymphoma

Follicular lymphoma (FL) is a slowly progressive disease and constitutes the second most common non-Hodgkin lymphoma. Biological factors, such as the tumor microenvironment and the host response, are determinants in the outcome of FL but the experimental data about microenvironment and tumor cells in FL are variable and contradictory. In this morphometric study, we analyzed by immunohistochemistry the cellular components of the tumor microenvironment and correlated these data with the microvascular vascular density in three different grades of FL lymph node biopsies, comparing the results to healthy lymph node controls. The results indicated a significant increase in the number of CD68(+) and CD163(+) macrophages in all three analyzed FL grades. Tryptase(+) mast cells resulted in an increase only in grade 1. PDL-1(+) cells, CD4- and CD8-lymphocytes number results were reduced in FL samples. The higher number of CD34(+) microvessels in the FL grades 1 and 2 of samples positively correlated with CD68(+) and CD163(+) cells, underlining the important angiogenic potential of this subset of macrophages.