In freshly excised lymph nodes of C57Bl/6 FoxP3‐EGFP mice with large tumours (250–430 mm3 B16F0 melanoma, 14–15 tumour growth period), T cells showed significantly increased NAD(P)H mean fluorescence lifetimes compared to T cells from tumour‐free mice and those with small tumours (40–250 mm3, 10–11 days growth period) due to prolonged lifetimes of protein‐bound NAD(P)H [130]. Here, FOXP3 is linked to neoplasm.