Enumerating FOXP3⁺ T cells within peritumoral and intratumoral sections using immunohistochemical analysis. Metastatic melanoma lesions from 20 patients were analyzed by immunhistochemistry to enumerate the number of FOXP3⁺ T cells in the intratumoral and peritumoral (stromal) areas in metastatic melanoma tumors. (A) CD4 (first column) and CD8 (second column) were visualized in pink and FOXP3 staining of nucleus was depicted in brown; ×40 magnification was used. (B) The percentage of FOXP3⁺CD4 T cells per total CD4 T-cell population in the intratumoral and peritumoral sections were calculated for each patient. The paired t test was used to compare between intratumoral and peritumoral sections.