A study of Foxp3+ regulatory T-cell in lesional skin of mycosis fungoides in comparison with some histological mimickers

Introduction Regulatory T-cells (Tregs) are essential to balance between proinflammatory and anti-inflammatory responses by protecting against autoimmune reactions. They have different roles in skin tumors, including cutaneous T-cell lymphomas. Foxp3 (forkhead box P3) is thought to be a reliable marker for Tregs. Contradictory results were reported in the literature when the density of Tregs in the skin of mycosis fungoides (MF, a type of cutaneous T-cell lymphoma) was compared with some pathologically mimicking inflammatory dermatoses. Patients and methods This is a comparative cross-sectional study of lesional skin biopsies from 36 cases of MF versus those from 36 cases of histopathological mimickers, including 10 cases of psoriasis, 10 cases of spongiotic dermatitis, and 16 cases of lichenoid dermatoses (10 with pityriasis lichenoides chronica and six with discoid lupus erythematosus). We compared the densities of Foxp3+ Tregs in relation to CD4+ cells in the epidermis and dermis of these groups using Foxp3 and CD4 monoclonal antibodies. Results The MF group showed a lower statistically significant difference as regards epidermal and dermal Foxp3/CD4+ ratios compared with the histologic mimicker group. Conclusion MF lesions showed a significantly lower density of CD4+ Foxp3+ Tregs compared with its histological mimickers, which might be attributed to their limited proliferation at the expense of malignant T-lymphocytes.