Background. Diffuse large B-cell lymphomas represent a heterogeneous group of tumors with a different origin, morphological findings and a variable clinical prognosis. These tumors have been recently classified into two prognostically relevant subgroups differing in the gene expression. The key genes suitable for routine diagnostics of DLBCL have not been yet identified. The aim of this work was to study changes and expression of several genes and proteins participating in the genesis of DLBCL. Methods and Results. We analysed a group of 31 patients with diffuse large B-cell lymphomas. Basic clinical data including follow-up of the patients were available. Tumors were examined by a panel of immunohistochemical reactions with antibodies against CD20, CD79a, BCL-2, BCL-6, CD10, Ki-67 and TP53. FISH was used to detect a translocation t(14;18)(q32;q21) and/or a break in BCL6 region (3q27) suggestive of a translocation with a variable translocation partner t(3;?). PCR was utilized to detect the translocation t(14;18) and a clonal rearrangement of heavy and/or kappa chain of the immunoglobin genes. Conclusions. The expression of BCL-2 protein appeared to correlate with a higher mortality rate. The expression of other proteins examined in the study did not correspond significantly with the clinical development of the disease. Tumors with follicular lymphoma as a component had significantly higher mortality rate than the tumors developing de novo. Moreover, higher mortality was evident in cases with higher values of the International Prognostic Index (IPI).

        Key words: diffuse large B-cell lymphoma, protein expression, clonality, translocations, prognosis, BCL-2.