ABCG2 and colorectal carcinoma: A Chinese study of ABCG2 protein expression analyzed with IHC (IHC; sparse information about antibodies: multiclonal anti-ABCG2 antibody; a FOUR score system based on the intensity of immunostaining and the number of positive cells was used, no separate scores for cytoplasmic versus membrane immunostaining) and including 60 cases of primary CRC showed that ABCG2 positive cells were mainly positioned in the front of the carcinomatous tissue (the invasion front) or between carcinomatous and non-carcinomatous margin tissue.