Cancerization describes a biological process where a broad area of cells within a tissue or organ undergoes abnormal changes, increasing the risk of cancer development. This phenomenon, sometimes called field effect or field change, signifies a pre-cancerous state. It involves cellular and tissue-level changes where cells have accumulated molecular alterations, including acquired genetic mutations and epigenetic modifications affecting large areas. These alterations make the tissue more susceptible to forming cancerous lesions over time.
What is Cancerization?
Cancerization involves cells accumulating molecular alterations, including genetic mutations and epigenetic modifications, across large areas. These changes may then progress to identifiable premalignant foci, such as dysplasia, and eventually to carcinoma in situ or invasive cancer. Common alterations in cancerization fields include reduced expression of DNA repair enzymes, reduced ability for programmed cell death (apoptosis), abnormal cell proliferation, and genomic instability.
The concept of cancerization suggests that a “field” of cells is affected, meaning a widespread, multifocal area, rather than just a single isolated spot. This field can contain cells with various genetic alterations, even appearing normal under a microscope. However, these seemingly normal cells can harbor molecular changes that indicate nearby or future tumors.
How Cancerization Develops
Cancerization arises from exposure to an injurious environment, often over an extended period. This exposure induces genetic or epigenetic aberrations in a cell or population of cells. If these alterations provide a survival advantage in the existing microenvironment, the precancerous cells will clonally expand, forming a field.
Chronic inflammation is a significant contributor to cancerization, creating an environment conducive to cellular changes. Prolonged exposure to carcinogens, such as ultraviolet (UV) radiation or chemicals in tobacco smoke, also leads to these alterations.
Persistent infections, like those caused by Human Papillomavirus (HPV) or Helicobacter pylori, can also promote cancerization by inducing genetic and epigenetic changes. Genetic predispositions, either inherited or acquired, play a role as well. These factors can collectively disrupt normal cellular functions, leading to uncontrolled cell growth and the accumulation of further mutations.
Where Cancerization Occurs in the Body
Cancerization can occur in various tissues and organs. Common examples include the skin, often seen as actinic keratoses due to chronic sun exposure. These lesions are considered an early form of squamous cell carcinoma in situ.
The cervix frequently experiences cancerization in the form of cervical dysplasia, often linked to persistent HPV infections. In the colon, adenomatous polyps are common examples of precancerous lesions that can develop into colorectal cancer. Lung tissue can also exhibit bronchial dysplasia, particularly in individuals with a history of smoking. Other sites where cancerization has been described include the head and neck, esophagus, breast ducts, and bladder.
From Cancerization to Cancer: Progression and Prevention
While cancerization indicates an increased risk, not all affected areas will progress to invasive cancer. The transition involves the accumulation of additional genetic mutations and epigenetic changes that further drive abnormal cell growth. This progression allows cells to invade surrounding tissues and potentially spread to distant sites.
Surveillance and monitoring are important for individuals diagnosed with cancerization. For example, regular colonoscopies can detect and remove precancerous polyps, thereby preventing colorectal cancer.
Preventative strategies to reduce the risk of progression include lifestyle modifications, such as maintaining a healthy diet and engaging in regular physical activity. Avoiding tobacco products and limiting alcohol consumption also significantly lowers cancer risk. Regular screenings and, in some instances, medical interventions like the removal of affected tissue, are also employed as preventive measures.