CD44 and cancer: CD44 is a plasma membrane glycoprotein that binds to hyaluronan (hyaluronic acid – HA) of the extracellular matrix and, as a cancer stem-cell marker,117 has been previously associated in OS with higher tumor grade,118 metastasis,119 and chemo-resistance.120–122 Our data suggest that these CD44+ stromal cells (of mesenchymal, fibroblast orgin123) likely play a role in TLS development by enhancing leukocyte infiltration and then coordinating subsequent B-cell rich follicle and T cell rich zone organization.