Precancerous

Precancerous, or premalignant, describes conditions in which cells show abnormal growth or architectural changes that increase the likelihood of developing cancer. These lesions are not cancerous themselves but carry an elevated risk of progression to malignancy over time. The term is used for various tissues and conditions in which dysplasia or in situ changes are identified.

Common examples include cervical intraepithelial neoplasia (CIN) detected on cervical screening, colorectal adenomas found during colonoscopy, actinic keratosis of the skin, and intraepithelial neoplasias of the vulva, vagina, or esophagus (such as Barrett's esophagus). Carcinoma in situ is a high-grade, noninvasive precancerous state in which malignant-appearing cells are confined by the basement membrane; invasion would define cancer.

Risk factors for precancerous changes overlap with those for cancer in general and include persistent infection with high-risk human papillomavirus (HPV), smoking, chronic inflammation, excessive ultraviolet exposure, and certain genetic factors. The likelihood of progression varies by tissue site and by the degree or grade of abnormality (for example, low-grade vs high-grade dysplasia).

Diagnosis relies on targeted biopsies and histopathologic examination, often supplemented by imaging or endoscopic assessment to determine extent. Management aims to remove or destroy the abnormal tissue or to monitor progression, depending on the lesion and its grade. Treatments can include surgical excision, ablation, topical therapies, or endoscopic procedures. Regular follow-up is important because some precancerous changes may regress, while others require ongoing surveillance to prevent progression to invasive cancer. Public health screening programs play a key role in early detection and prevention.