Tumors are abnormal tissue formations. We differentiate between benign and malignant tumors. In the first case tissue formations of the tumor are clearly separated from the surrounding tissue, do not infiltrate it and don’ t generate any metastases. In the second case the malignant tumor infiltrates and destroys the surrounding tissue and generates metastases. Important imaging techniques in order to diagnose the tumors are computed tomography, magnetic resonance imaging, digital mammography and virtual colonoscopy.