Evidence that an identical T cell clone in Skin and peripheral blood lymphocytes is an independent prognostic factor in primary cutaneous T cell lymphomas

The monoclonality of the T cell receptor gamma -chain gene was analyzed by polymerase chain reaction in skin and blood specimens of 85 patients with c utaneous T cell lymphomas including 67 mycosis fungoides, seven Sezary synd romes, and 11 CD30-nonepidermotropic cutaneous T cell lymphomas. A cutaneou s T cell clone was detected in 69% of mycosis fungoides and 100% of Sezary syndromes. This frequency varied according to the clinical stage: 57% in ea rly stages (Ia-IIa) to 96% in advanced stages (IIb-IV, Sezary syndrome). A peripheral blood T cell clone was detected in 42% of early stages and in 74 % of late stages but was identical to the cutaneous one in 15% and in 63%, respectively. A significant association between initial clinical stage and T cell monoclonality was observed. In nonepidermotropic cutaneous T cell ly mphomas, T cell monoclonality was detected in 55% of skin and 36% of blood samples. Univariate and multivariate analyses showed that, besides the init ial clinical stage, an identical cutaneous and blood T cell clone was an in dependent prognostic factor for disease progression of mycosis fungoides/Se zary syndrome (hazard ratio 3.4, 95% confidence interval 1.4-9.9). Parallel polymerase chain reaction study of skin and blood specimens may therefore provide an initial prognostic marker that could help to monitor therapeutic strategies. A fully prospective study, with simultaneous therapeutic trial s, needs to be done to confirm our findings and to include treatment variab les in the statistical analysis.