The intermediate stage from normal tissue to the development of cancer is called precancerous lesion. Benign tumors can sometimes be transformed into malignant, called benign tumor malignant transformation, such as fibroma can be transformed into fibrosarcoma. Some diseases can be easily transformed into malignant tumors, such as atrophic gastritis can develop into gastric cancer; junctional nevus can develop into malignant melanoma, these diseases are called precancerous diseases or precancerous lesions. Common tumors can be cancerous from the following diseases: Stomach cancer – gastric ulcer (2% to 8% cancer rate), atrophic gastritis. Bowel cancer – intestinal polyps (40% to 50% cancer rate), chronic ulcerative colitis. Penile cancer – cryptorchidism, circumcision (85% to 100% cancer rate) Cervical cancer – cervical erosion (20%-35% cancer rate) Ovarian cancer – ovarian cysts (50% to 75% cancer rate) Uterine body cancer – uterine fibroids. Thyroid cancer – adenoma of the thyroid gland (20% cancer rate) Breast cancer – cystic hyperplasia of breast (20% to 50% cancer rate), fibroadenoma of breast (26% cancer rate). Skin cancer – nevus, chronic ulcers, white spots, scarring, radiation dermatitis, heliosis, epidermoid cysts. Mucosal carcinoma – white spots on mucous membranes, chronic inflammation, ulcers, or papillary protrusions Choriocapillary epithelial carcinoma – chylothorax. Hepatocellular carcinoma – migratory hepatitis, liver cirrhosis, and those with family history. Lung cancer – long-term chronic bronchitis, adenoma, persistent tuberculosis. Prostate cancer – chronic prostatitis.