Intralesional therapy with anti-CD20 monoclonal antibody rituximab: local and systemic efficacy in primary cutaneous B-cell lymphoma.

Rituximab (MabThera, Roche) is a chimeric monoclonal antibody directed against the CD20 antigen. Its efficacy and safety were first demonstrated in the treatment of systemic B-cell lymphomas. We report the use of intralesional injections of rituximab into some but not all cutaneous lesions in a patient with multiple primary cutaneous follicular centre B-cell lymphoma. This treatment resulted in tumour regression, even of the lesions that had not been injected. We therefore hypothesize that there is systemic diffusion of rituximab from injected sites despite the low doses injected locally, or the induction of a specific antitumour immune response acting systemically.