Peripheral blood T-cell clonality in mycosis fungoides and nonlymphoma controls.

In mycosis fungoides (MF), T-cell clonality is reported in about 90% of skin and 40% of blood samples. However, identity of blood and cutaneous T-cell clone and prognostic relevance of blood T-cell clonality remain controversial. By PCR/fluorescence fragment analysis with estimation of clonal fragment lengths and relative peak heights, we objectively identified T-cell clonality unrelated to malignant lymphoproliferation in healthy donors (5/38), autoimmune dermatoses (3/8), and nonlymphoma skin cancer (9/39). This T-cell expansion of undetermined significance (TEXUS) was also found in 8/64 MF patients. Dissemination of neoplastic cells into blood, as identified by identical clonal fragment lengths in blood and skin, was detected in 23/64 MF patients. When monitoring for progression at TNM stage for a mean of 45.7 months, univariate analysis identified age of >60 years and detection of a related blood T-cell clone to be of prognostic relevance, whereas detection of TEXUS, sex, TNM stage at initial diagnosis, and detection of a cutaneous T-cell clone were irrelevant. Although multivariate analysis was not possible, further stratification clearly indicated an age of >60 years to be the predominating prognostic factor. In conclusion, investigation of T-cell clonality in skin and blood samples at the initial diagnosis cannot predict the clinical course of MF and the occurrence of TEXUS should be considered when assessing blood T-cell clonality.