Colon cancer. Coloured scanning electron micrograph (SEM) of a freeze-fractured section through the colon (large intestine) wall of a patient suffering from colonic cancer. Tumour cells (rounded structures, upper frame) are seen on the mucosal lining of the colon. These metastatic cells are spreading down through the sub-mucosa (lower frame), the layer that lies beneath the lining of the colon. This patient is suffering from an adenocarcinoma, a malignant tumour derived from glandular structures in the colon wall. The cancer may be treated by surgical removal of the affected area. Magnification unknown.