CTLA4 and cancer: Because these techniques are best applicable to unfixed tissues which is unavailable from most tumors in routine praxis, studies on CTLA-4 in cancer mostly involved limited numbers of samples from frequently occurring tumor entities such as malignant melanoma (n = 56–470)8,9, breast (n = 928–1217)10, colorectal (n = 439–1003)10–12 and renal cell cancers (n = 813–928)10,12,13.