Colon cancer. Immunofluorescent light micrograph of human colon cancer cells. The nucleus of each cell is pink, surrounded by a fibrous mass of green tubulin, a protein used by cells during cell division. At upper right and lower left two cells are seen undergoing mitotic cell division. The chromosomes of these are condensed and stained blue, surrounded by red cytoplasm and green tubulin. Such large nuclei and cell divisions are characteristic of cancer cells. Colonic cancer is a common form of cancer. Immunofluorescence is a technique that uses antibodies to attach fluorescent dyes to specific parts of a cell. Magnification: x374 at 4.5x6cm size.