T‐cell receptor gene rearrangement analysis of sequential biopsies in cutaneous T‐cell lymphomas with the Biomed‐2 PCR reveals transient T‐cell clones in addition to the tumor clone

Detection of a dominant T‐cell clone by T‐cell receptor (TCR) gene rearrangement analysis is often essential for the diagnosis of cutaneous T‐cell lymphomas (CTCL). The occurrence of T‐cell clones in addition to the diagnostic T‐cell clone during the course of CTCL has been reported, but the data of these studies have been contradictory. We retrospectively evaluated the data of 114 lesional skin biopsies from 26 patients with Mycosis fungoides and two patients with primary cutaneous anaplastic large cell lymphoma, which were analysed with the standardized Biomed‐2 PCR for the TCRγ and TCRβ locus. A dominant T‐cell clone was repetitively detected in 93% (26/28) of patients. Additional T‐cell clones appeared temporarily in 39% (11/28) of patients. Correlation with the clinical data did not show an association of the presence of additional T‐cell clones with age, number of treatments, progression of disease or survival. Our findings demonstrate that a persistent T‐cell clone, most likely the disease causing tumor clone, is detectable in almost all CTCL patients. In addition, transiently appearing T‐cell clones frequently occur during the course of disease. The biological relevance of these additional clones has still to be determined. However, it is important to take the possibility of additional T‐cell clones into account for diagnostic analyses.