Background: Apart from routine histological and immunohistochemical examination the immunophe¬notypization by flow cytometry is a very helpful and potent auxiliary method in diagnosis of malignant lym¬phomas (ML). The first necessary and unevitable step for flow cytometric examination is to obtain a repre-sentative cell suspension that can prove to be rather problematic in čase of cutaneous T-cell lymphomas. Methods and results: In order to isolate lymphoid cells from a skin excision the enzymatic digestion is ušed. Yet, in čase of poor tissue infiltration the flow cytometry fails because of the small amount of lym-phocytes in the cell suspension. We háve analyzed 66 samples from 17 patients (20 from skin, 20 from bone marrow and 26 from peripheral blood) during primary diagnosis, staging and restaging of cutaneous T-cell lymphoma. The flow cytometry from skin was diagnostic for T-cell lymphoma in 9 cases, in 1 čase the fin-ding was suspicious for lymphoma, in 4 cases the examination did not contribute to the diagnosis. In 6 cases the tissue was only sparsely infiltrated by lymphocytes and optimal cell suspension was not obtained. During staging and restaging the examination of the bone marrow samples in 14 cases did not reveal any lymphoma either morphologically or by flow cytometry, in 3 cases the infiltration was proved by both me-thods. In 3 cases the flow cytometry proved the bone marrow infiltration in špite of a negative histology and in 3 cases the flow cytometric results were suspicious for infiltration while histological finding was negative in 2 cases and unequivocally positive in 1 čase. In the peripheral blood samples the tumor cells were detec-ted in 3 cases, the finding was suspicious in 2 cases and negative in 21 cases. Conclusion: The flow cytometry is of vital diagnostic importance especially in cases of massive cutane¬ous infiltration, but lymphoid tissue seems to be a better diagnostic materiál. If the infiltration of the tissue is not massive, the number of lymphocytes in suspension is insufficient, and the examination is not conclu-sive. In addition, if the aberrant immunophenotype of tumor cells is observed, the method is ideál for moni¬toring a minimal residual disease.

        Key words: cutaneous T-cell lymphomas - mycosis fungoides - flow cytometry - Sézary syndrome