The presence of specific environmental risk factors should prompt a search for preneoplastic lesions. Major aspects of cancer prevention include the identification of such lesions, removal of those at high risk for neoplastic transformation, and efforts to reduce patient exposure to agents that may be responsible for the preneoplasia. Preneoplastic lesions have been detected in most organ systems. Such lesions have been demonstrated in the bronchial mucosa by fiberoptic bronchoscopy, and their incidence correlates with the amount of cigarette smoking. Similar preneoplastic changes have been observed in the oral and oropharyngeal mucosa.
Some patients are at a significantly increased risk for recurrent preneoplasia.
For example, in patients who have had cancer of the head and neck that has been cured, the increased risk of a new primary tumor developing in that area may approach four percent a year. Some preneoplastic lesions in the oral cavity, such as leukoplakia, have a two to three percent risk of becoming neoplastic, whereas the much less common erythroplasia carries a 60 percent risk of progressing to neoplasia. Chronic cystic mastitis had previously been considered a preneoplastic lesion that could develop into breast carcinoma. More recently, however, it has been found that only the 10 to 20 percent of patients with cystic disease who exhibit hyperplasia and nuclear atypia on biopsy are at an increased risk for breast cancer. Adenomatous polyps of the colorectum represent premalignant lesions, and the number and size of such polyps correlate with the risk of neoplasia.