FOXP3 is a forkhead transcription factor family member involved in T-cell regulation, activation and differentiation. FOXP3 has been shown to be a master control gene for the development and function of CD4 /CD25 regulatory T-cells. In IHC, FOXP3 has been shown to be a specific marker for adult T-cell leukemia/lymphoma (1). In melanoma and in breast and lung cancers, high numbers of circulating regulatory T-cells have been associated with disease progression (2-5). Conversely, the infiltration of FOXP3 regulatory T cells into invasive tumors has also been reported to be associated with survival in a variety of cancers (2-7). In colon cancers, a high frequency of FOXP3 infiltrates has shown to be a positive indicator (6-7). Patients with high FOXP3 expression in Crohn’s disease have shown a better response to infliximab therapy (8). In allography recipients, FOXP3 cell levels may also be useful in improving post-transplant management (9).