Detection of clonal T-cell receptor gene rearrangements in the peripheral blood of patients with mycosis fungoides/Sezary syndrome.

Involvement of the peripheral blood in mycosis fungoides/Sezary syndrome (MF/SS) has a significant impact upon prognosis, but it is often difficult to distinguish circulating cells of MF/SS from atypical reactive lymphocytes. We compared the standard morphologic method of identifying leukemic cells, the Sezary preparation, to a genotypic method using Southern blot analysis of T-cell receptor gene rearrangements in concurrent blood samples. We studied 26 MF/SS patients, five of them in remission, together with five controls from cases of various non-MF/SS skin diseases. Six of 26 MF/SS patients had morphologically atypical circulating leukocytes (3%, 4%, 5%, 14%, 16%, 19%). Seven of 26 MF/SS patients had clonal T-cell receptor gene rearrangements, including the four patients with the greatest percentages of atypical cells and three patients lacking atypical cells. Six of seven patients had skin disease at the time of sampling, including three with erythroderma, two with generalized thick plaques, and one with generalized patches, while one patient was in clinical remission. All five controls lacked morphologic and genotypic evidence of atypical or clonal T-cells. Relative to genotyping, in our series the Sezary preparation was less sensitive and less specific. There were three apparent false negative results in the Sezary preparations, and two potential false positive (patients with 3% and 4% atypical leukocytes); however, there was agreement between the two techniques in most cases. We conclude that gene rearrangement studies may provide an effective test with which to assess the peripheral blood of MF/SS patients.