RecruitingDrug trialStudy to Evaluate the Response to Treatment With Mosunetuzumab in Relapsed/Refractory Follicular Lymphoma (FL) After at Least Two Lines of Therapy, Within the Compassionate Use Program (CUP).Retrospective, multicenter observational study to evaluate the response to treatment with Mosunetuzumab in relapsed/refractory Follicular Lymphoma (FL) after at least three lines of therapy, within the Compassionate Use Program (CUP).