Dividing breast cancer cells. Coloured scanning electron micrograph (SEM) of breast cancer cells during anaphase, the third stage of mitotic cell division. During mitosis, the nuclear material of a cell divides, followed by separation of the cytoplasm and cell organelles to form two daughter cells. During the anaphase stage of mitosis, the pairs of chromosomes separate into chromatids that travel along spindle fibres to opposite ends of the cell. Cytokinesis or cell division begins to occur, causing the cell to become narrow in the middle. Cancer cells divide rapidly and chaotically, and may clump to form malignant tumours. The tumours often invade and destroy surrounding tissues. Breast cancer is the most common form of cancer in women. Treatment involves surgical removal of the tumour, often combined with radiotherapy and chemotherapy. Magnification: x2200 when printed 10cm wide.