Background and design: We used the amplification of junctional V (variable)-J joining sequences of the rearranged T-cell receptor gamma (TCR gamma) genes by polymerase chain reaction for rapid and sensitive detection of a clonal T-cell population in a total of 51 skin specimens obtained from 45 patients with mycosis fungoides, five patients with Sézary syndrome, and 29 patients with chronic inflammatory dermatoses.
Results: A clonal TCR gamma gene rearrangement was present in all tumors (3/3, 100%) and in most infiltrated plaques (16/22, 73%) and erythrodermas (10/12, 83%). In the patch stage, a clonal subset was found in more than half of the cases (8/14, 57%), whereas no clonality was observed in the controls. We also amplified the V-J sequences of the Igh locus coding for the heavy chain of immunoglobulins, without evidence of clonal rearrangement. These data were compared with those from in situ immunophenotypic analysis. Moreover, by using the same assay with successive dilutions of standard clonal T-cell DNA, a semiquantitative study of the T-cell clone was carried out in some cases. The highest ratios of clonal DNA were observed in advanced stages.
Conclusions: These data validate polymerase chain reaction V gamma-J gamma as a rapid, sensitive tool that can be used in the routine analysis of clonality in cutaneous lesions of mycosis fungoides and in the early diagnosis of mycosis fungoides and Sézary syndrome. Semiquantitative studies suggest that the malignant T-cell clone follows a selective process during the course of the progressive form of mycosis fungoides.