This study is a regulatory post marketing surveillance in Japan, and it is a local
prospective and observational study of patients who have received Zevalin for relapsed or
refractory, CD20+, low grade B-cell non-Hodgkin's lymphoma and Mantle cell lymphoma. The
objective of this study is to assess safety and efficacy of using Zevalin in clinical
practice. This study is also all case investigation of which the enrollment period is five
years, and all patients who received Zevalin will be recruited and followed 13 weeks after
the administration.