AbstractUsing monoclonal T cell antibodies, we compared T cell subsets of skin infiltrates with the nuclear contour index (NCI) of pan T cells of skin infiltrates from erythematous, plaque and tumor lesions in the same patients with mycosis fungoides (MF). In all lesions, the majority of the skin‐infiltrate population were T cells; helper T cells were especially dominant in the plaque and tumor lesions. The NCI of the T cells in skin infiltrates increased in parallel with advancing stages of the lesions in the same patient. The NCI data for T cell and T cell subsets in different stages of lesions in the same patient were similar to data from different stages of lesions in different patients. Therefore, even in tumor stage patients, topical treatment should be selected in accordance with the cytological stage of their lesion