FOXP3 in sequential biopsies of progressive mycosis fungoides

A recent report has suggested that the numbers of regulatory T cells correlate with stage of disease and prognosis in mycosis fungoides (MF). To evaluate the role of FOXP3+ Tregs in different stages of MF, we investigated sequential biopsies in 14 patients with patch/plaque and subsequent tumor stage using FOXP3 antibody. Our data neither show a significant difference in the percentage of FOXP3+ cells between patch/plaque and tumor stage biopsies of MF nor demonstrate a predictable shift of Tregs in the course of disease progression. Additionally, we could observe FOXP3-expressing neoplastic cells in 4 patch/plaque stage biopsies, where they represented almost 100% of the epidermotropic infiltrate. Only in one of these patients, FOXP3+ cells could also be detected in the tumor stage biopsy, indicating that FOXP3 expression can be acquired or lost during the course of the disease, comparable to other phenotypic markers.