Two cases of malignant non-Hodgkin's lymphoma arising in an Albrecht-Arzt-tumour are reported. In the first case a centroblastic-centrocytic lymphoma in a palatinal cystadenolymphoma of a 64-year-old female is described. In the other case a centroblastic lymphoma developed in an Albrecht-Arzt-tumor of the submandibular region in an 82-year-old man. The occurrence of a high-grade malignant lymphoma in cystadenolymphoma has not been reported in the literature so far.

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Lymphoepithelioid lymphoma (Lennert's lymphoma) was first described as a special variant of Hodgkin's disease. This lesion is characterized by a high percentage of epithelioid and T cells and rarely contains the classical Hodgkin's/Reed-Sternberg cells. Cytogenetic abnormalities indicate that Lennert's lymphoma is of T cell origin. In the present study, immunohistochemical investigation of four cases of Lennert's lymphoma revealed two major cell populations of T cells that predominantly express the helper-inducer phenotype and Ki-M6- and Ki-M8- positive macrophages and epithelioid cells. Double-staining experiments for the detection of cell surface antigens and the proliferation- associated antigen Ki67 showed that only the CD4-positive cells (helper- inducer T cells) were proliferating. Examination of the DNA of these Lennert's lymphoma samples also indicated that monoclonal rearrangement of the T cell receptor beta-chain genes has occurred, whereas the immunoglobulin heavy- and kappa-chain genes remained in germline configuration. Our results strongly suggest that Lennert's lymphoma is a CD4-positive T cell lymphoma.