Posttransplant lymphoproliferative disorders (PTLDs) present a wide clinicopathological spectrum, varying from the usual Epstein-Barr virus (EBV)-driven infectious mononucleosis-type polyclonal proliferations to EBV-positive or EBV-negative proliferations indistinguishable from overt lymphomas that occur in immunocompetent individuals. PTLDs characteristically have a predilection for extranodal sites and association with EBV.These disorders are usually B-cell type, although T-cell and rare cases involving both T- and B-cell types have also been described. The initial treatment consists in decreasing the immnosupressive therapy, usually with favorable results. The authors report on a rare case of a 19-year-old girl, with post-renal transplantation EBV-associated polymorphic lymphoproliferative gingival ulcerated lesions. To the best of their knowledge, this is the first case described in the English-language literature of polymorphic PTLD involving both B-cell and T-cell lineages, with an unusual immunoprofile affecting the mouth. The authors warn that this condition could be easily misdiagnosed as malignant lymphoma if not properly recognized.