Breast cancer cells. Coloured scanning electron micrograph (SEM) of freeze-fractured cancerous breast tissue showing breast cancer cells (across upper frame). Their irregular and ragged appearance is typical of cancer cells, which divide rapidly and chaotically. They can then 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 unknown.