The cellular composition of the in situ analyzed colorectal specimen (n = 27/30) was assessed by flow cytometry using the epithelial cell markers: CD326, which reliably stains almost all CRC cells; MHC class II as marker of antigen presenting cells; CD3 for T cells; and a lineage panel consisting of CD19, CD20, and CD21 to detect B cells. The gene discussed is CR2; the disease is colorectal carcinoma.