We report the use of Atomic Force Microcopy (AFM) in combination with Fluorescence Microscopy (FM) for the investigation of non-Hodgkin's type B cells lymphoma after antibody treatment. Rituximab is used in the treatment this cancer type. It is a chimeric monoclonal antibody directed against the protein Cluster of Differentiation 20 (CD20), which is expressed on mature B cells, including the B cell lymphoma surface. We applied anti-CD20 antibody to the B lymphoma cells that was labeled with fluorophore. Simultaneous imaging was then performed by both FM and AFM. Immunofluorescence imaging confirms the binding of Rituximab to the CD20 protein; while the AFM imaging revealed changes in lymphoma cells in terms of mean cell height and cell surface roughness. In addition, our AFM based nanomanipulation system can assist in the analysis of mechanical property of the cell by recording the force-displacement curves at the cell surface. AFM imaging and measurements may provide biomarkers of cell behavior and may facilitate the treatment of lymphoma clinically as a pretest to determine the effectiveness of the drug Rituximab on lymphoma cells from individual patients.