Background. Diagnostic approach to non-Hodgkin’s lymphomas requires a combination of laboratory methods. Methods used in morphology constitute the basis of the diagnostics; in many instances it is necessary to combine them with methods of molecular genetics. The latter method plays a key role in the detection of B cell clonality using identification of the rearrangement of IGHand/or IGKgenes and in detection of the chromosomal translocations specific for some lymphomas. Methods and Results. Using PCR we investigated 113 patients with malignant B cell lymphomas of different types (follicular – FL, mantle cell – MCL, small cell – CLL/SLL, diffuse large cell – DLBCL). We established the IGH gene clonal rearrangement in 85 % of the cases (96/113), and the clonal rearrangement of the IGK gene in 58,3 % patients (42/72). Combination of both approaches (IGH and IGK) revealed a positive result in 90,3 % (102/113). The highest yield was rendered in patients with CLL/SLL and with MCL (100 %), and it was 86 and 87 % in cases with FL and DLBCL. Conclusions. The detection of clonality in lymphomas helps to distinguish a malignant disease from polyclonal hyperplastic and lymphoproliferative disorders of B cells. The recognition of clonal rearrangements of the IGH and IGK genes serves for a long term monitoring of the disease activity in cases in which there are no other molecular markers available. The demonstration of lymphoma characteristic translocations is relatively specific and useful but at present its usefulness is reduced in cases with variable breakpoint regions.

        Key words: non-Hodgkin’s lymphomas, clonality, immunoglobulin genes, PCR.