the distinct subset of primary cutaneous diffuse large b cell lymphoma , leg type ( pcdlbcl - lt ) is characterized by frequent recurrence , extracutaneous dissemination and a high mortality rate . to improve patients outcome a monoclonal antibody , rituximab , directed against the b cell antigen cd20 , was recently approved for the treatment of b cell lymphomas . in the present case , a wheal attack developed particularly at the site of tumor lesions , and those tumor lesions subsequently disappeared after rituximab monotherapy . only a few cases of rituximab - related urticarial reactions have been reported in patients treated for b cell lymphoma [ 3 , 4 , 5 , 6 ] . therefore , we would like to report a rare case and discuss the possible mechanism underlying rituximab - related urticarial reaction , which may improve the understanding of an unrecognized clinical effect of rituximab on tumors . a 73-year - old male presented to our department in january 2010 with a 7-year history of erythematous skin patches on his left lower leg which had not improved after the use of topical steroids . at initial physical examination , erythema and red - to - brown - colored , various - sized cutaneous nodules were found on the bilateral lower legs ( fig . histological study showed dense infiltration of lymphoid cells with irregular nuclei in the superficial and deep dermis ( fig . 1b , c ) , and immunohistological staining revealed that most of the infiltrating lymphoid cells were positive for cd20 ( fig . whole body imaging studies and bone marrow histopathology did not detect metastatic or disseminated disease . based on these results , we diagnosed the patient with pcdlbcl - lt , which was stage ib according to the who - eortc classification . based upon the standard chemotherapy regimen , we administered biweekly combination chemotherapy with rituximab , pirarubicin , cyclophosphamide , vincristine and prednisolone ( r - thp - cop ) . within 2 h after the initial administration of intravenous rituximab , he noticed urticaria along the tumor lesions ( fig . 1e ) , and these urticarial lesions disappeared rapidly following treatment with an oral antihistamine . four weeks after the second course of r - thp - cop chemotherapy , the tumor lesions had completely remitted ( fig . 1f ) , which was confirmed by no evidence of cd20-positive lymphoid tumor cells in his skin ( fig . 1 g ) . he has remained in remission for 5 years under clinical observation . we experienced a rare case with a wheal attack that developed on the sites of pcdlbcl - lt tumor lesions after the induction of rituximab therapy . rituximab is a chimeric monoclonal antibody consisting of the variable region of murine anti - cd20 and the human igg1( ) heavy and light chain constant regions , and is known to successfully treat patients with cd20-positive indolent and aggressive b cell non - hodgkin lymphomas . the three main mechanisms known to underlie the anti - tumor effects of rituximab are complement - mediated cytotoxicity ( recruiting neutrophils through the release of chemotactic c3a and c5a fractions ) , antibody - dependent cell - mediated cytotoxicity ( especially that mediated by natural killer cells ) and/or direct cytotoxicity [ 7 , 8 , 9 ] . in addition , it was reported that the levels of c3 , c4 and cytokines such as il-6 , il-8 and tnf- were increased within 30 min after the administration of rituximab in patients with low - grade non - hodgkin 's lymphoma . based on this evidence , it has been supposed that rituximab is somehow recognized by the immune system of the patient , and activation of the above three pathways might stimulate mast cells , followed by an increase in blood vessel permeability exclusively in both the urticarial and tumor lesions . in the present case , we could not examine the complement level and mast cell infiltration on the active wheal lesions . further accumulation of similar cases and their detailed observations would help clinicians understand the exact mechanisms underlying the development of rituximab - related wheal attacks in patients with cutaneous lymphoma .
an elderly male noticed urticarial patches corresponding to cutaneous b cell lymphoma lesions after rituximab treatment . along with the resolution of urticaria , the lymphoma lesions completely remitted without recurrence . in this communication , we present an interesting case and the pathophysiological findings of a wheal attack in a case with tumor remission following systemic treatment with rituximab , a monoclonal anti - cd20 antibody .