Precancerous cells are abnormal growths that have the potential to progress into invasive cancer over time. These cells are not yet malignant, meaning they cannot spread to distant parts of the body, but they signal an elevated risk. Detecting and removing these lesions is a highly effective strategy for cancer prevention, often leading to a complete resolution of the risk.
Defining Precancerous Cells and Risk
Precancerous cells are referred to as dysplasia or intraepithelial neoplasia, indicating cellular changes that deviate from normal appearance and growth patterns. Dysplasia describes cells that look abnormal under a microscope, with severity ranging from mild (low-grade) to severe (high-grade). Mild dysplasia means only a small fraction of the tissue layer is affected, while severe dysplasia means most or all of the tissue layer is composed of abnormal cells.
The most advanced form of precancerous growth is called carcinoma in situ (CIS), representing full-thickness abnormality of the tissue lining (epithelium). CIS is distinguished from invasive cancer by the status of the basement membrane, a thin layer separating the epithelium from underlying tissue. In precancerous conditions, this membrane remains intact, preventing abnormal cells from invading deeper structures and spreading.
The terminology for these lesions varies depending on the organ system, such as cervical intraepithelial neoplasia (CIN) or adenomatous polyps in the colon. The risk of progression is directly tied to the lesion’s grade; a high-grade lesion, like CIN 3, carries a higher probability of becoming invasive cancer than a low-grade lesion, like CIN 1. This inherent risk drives the decision to intervene with treatment.
Determining the Need for Removal
The decision to remove precancerous cells is not always immediate and depends on a careful assessment of the lesion’s potential for progression. Clinicians weigh several factors, including the grade of the lesion, its location, the patient’s age, and their overall health status. Low-grade lesions, such as CIN 1 in the cervix, frequently regress on their own, often clearing up as the body’s immune system eliminates the underlying cause, such as a viral infection.
For these lower-risk lesions, a strategy known as active surveillance, or “watchful waiting,” is often preferred over immediate intervention. This involves regular, closely spaced follow-up examinations, such as repeat screenings or biopsies, to monitor for any signs of progression. This approach helps avoid overtreatment and potential side effects from unnecessary procedures, especially in younger patients who may have future fertility concerns.
Conversely, high-grade lesions, such as CIN 2 or CIN 3, or severe dysplasia, require removal or destruction. The risk of these lesions progressing to invasive cancer is high, warranting intervention since treatment at the precancerous stage is highly successful at preventing malignancy. In some cases, such as a high-risk cervical screening result, treatment may be expedited without a preceding biopsy to reduce the risk of patients being lost to follow-up.
Specific Medical Procedures for Eradication
The procedures used to eradicate precancerous cells fall into two main categories: ablative techniques, which destroy the abnormal tissue in place, and excisional techniques, which physically remove the tissue. The choice of procedure depends on the lesion’s location, size, and the need for a tissue specimen for final diagnosis.
Ablative Procedures
Ablative techniques destroy the precancerous cells using extreme temperatures or energy, but they do not provide a tissue sample for further pathological analysis. Cryotherapy is a common ablative method, especially for cervical precancer, where a cryogenic gas is used to rapidly freeze and destroy the abnormal tissue. This process creates an “iceball” that reaches a depth of several millimeters to ensure complete destruction of the lesion.
Thermal ablation, also known as thermocoagulation, uses a heated probe to destroy the tissue. This method is used for treating cervical lesions, particularly where complex excisional procedures are less accessible. Laser ablation precisely removes tissue by vaporization and is useful for lesions extending onto the vagina.
Excisional Procedures
Excisional techniques physically cut out the abnormal tissue, which is then sent to a laboratory for detailed examination by a pathologist. This provides a definitive diagnosis and confirms that the margins of the removed tissue are clear of abnormal cells, a significant advantage over ablative methods. The most common excisional procedure for cervical precancer is the Loop Electrosurgical Excision Procedure (LEEP), also known as Large Loop Excision of the Transformation Zone (LLETZ).
LEEP uses a thin wire loop with an electrical current to quickly and precisely slice away a cone-shaped piece of tissue from the cervix. For larger or deeper lesions, a Cold Knife Conization (CKC) may be performed, which uses a scalpel to remove the tissue and requires general anesthesia. Surgical excision is the standard approach for removing precancerous growths like severe colon polyps or high-grade skin lesions, ensuring that the entire abnormal area is removed with a margin of healthy tissue.
Topical and Non-Invasive Treatments
For certain precancerous skin lesions, such as actinic keratosis, non-invasive topical treatments may be used. These methods include specialized creams containing agents that function like chemotherapy or the use of photodynamic therapy. Photodynamic therapy involves applying a light-sensitizing drug to the lesion, which is then activated by a specific wavelength of light to destroy the abnormal cells. These treatments are localized and reserved for lesions on the surface of the skin or other easily accessible areas.
Post-Treatment Surveillance and Prevention
Following the removal of precancerous cells, a structured follow-up plan is implemented to monitor for recurrence and ensure the treatment was fully successful. Post-treatment surveillance protocols typically involve repeated screenings, often combining cytology and Human Papillomavirus (HPV) testing for cervical lesions. The first follow-up screening is usually scheduled six to twelve months after the procedure, with subsequent screenings occurring at regular intervals.
Successful removal does not eliminate the underlying risk factors that contributed to the initial formation of the lesion. Even after effective treatment, there is a small risk of new precancerous cells forming, which necessitates consistent, long-term monitoring. The risk of recurrence is low, with successful treatment rates exceeding 95% for cervical precancer.
Prevention strategies focus on mitigating the known causes of precancerous lesions. For HPV-related precancers, such as those in the cervix, anus, or throat, vaccination against HPV is a highly effective primary prevention method. Lifestyle modifications, such as smoking cessation and maintaining a healthy diet, can also help lower the risk of developing new lesions across various body sites, including the mouth, lung, and colon.