Ibritumomab tiuxetan is a radiolabled monoclonal antibody that targets B-cell non-Hodgkin lymphoma tumor cells. Yttrium-90 (Y-90), the radioisotope used to deliver the therapy, may act as a vesicant, potentially causing severe tissue damage if extravasation occurs. Particularly important to nurses is that Y-90 may not show signs or symptoms of extravasation until weeks or months after the IV injection. A case study of a man with B-cell non-Hodgkin lymphoma presented in this article shows the progression of the extravasation and steps taken to treat and eventually heal the extravasation site. Included is information about ibritumomab tiuxetan treatment, administration, eligibility criteria, and guideline recommendations for extravasation.