Background: Early Mycosis fungoides (MF) is difficult to distinguish from other benign inflammatory dermatoses. We evaluated clonal T-cell receptor (TCR) gene rearrangement by polymerase chain reaction (PCR) as a surrogate to histological diagnosis in early MF. Methods: Twenty paraffin -embedded skin biopsies from 9 patients diagnosed with MF were included. Two multiplex PCR encompassing various V and J讪 regions were used to detect TCR讪 gene rearrangements. Histological diagnoses were categorized as “diagnostic”, “consistent”, suggestive” ,or “non-diagnostic”. We compared TCR PCR results with histological parameters to determine the differences between PCR-positive and PCR-negative groups. Results: TCR PCR was positive in 53% (8/ 15) of the patch stage, in 100% (2/2) of the plaque stage, and in 100% (3/ 3) of the tumor stage. TCR讪 PCR was positive in 50% (4/8) of the specimens in both the diagnostic and consistent of MF groups; 71% (5/7) in the suggestive of MF group. We found that inflammation was more severe in PCR-negative specimens. Papillary dermal fibrosis was common, and differed significantly between PCR-positive and PCR-negative groups ( P = 0.01). T-cell monoclonality was detected in one non- diagnostic lesion in a patient with psoriasis and MF
