Squamous cell carcinoma (SCC) is not contagious and cannot be transmitted from one person to another. This common form of skin cancer originates in the squamous cells, which are the flat cells making up the upper layers of the epidermis. The disease results from damage to the cellular structure and is not caused by an external, infectious agent like a bacterium, virus, or fungus.
Understanding Squamous Cell Carcinoma
Squamous cell carcinoma is the second most common form of skin cancer, arising from an uncontrolled growth of abnormal cells in the middle and outer layers of the skin. These cells are known as keratinocytes, and they make up the majority of the epidermis. The disease begins when the DNA within these cells is damaged, leading to rapid, disorganized cell division.
Cutaneous SCC often appears on sun-exposed areas of the body, such as the face, ears, neck, and hands. It typically presents as a firm, red nodule or a rough, scaly patch that may crust, bleed, or fail to heal over several weeks. While usually localized to the skin, if left untreated, SCC has the potential to grow deeper and spread to other parts of the body.
Why Cancer Cannot Be Contagious
Cancer is fundamentally a disease of a person’s own mutated cells, representing an internal biological malfunction, not an external infection. For SCC to be contagious, the malignant cells would need to survive transfer between individuals, which is biologically impossible in humans.
A healthy recipient’s immune system immediately recognizes foreign cells, including cancer cells from another person, as non-self. The body’s defense mechanisms destroy these foreign cells before they can establish a blood supply or begin to grow. The only known exception involves extremely rare cases of organ or tissue transplantation where cancer is transferred from the donor, but this occurs only because the recipient is intentionally taking immunosuppressive drugs to prevent organ rejection.
Some cancers, including specific types of head and neck SCC, are linked to the Human Papillomavirus (HPV) infection. The virus itself is contagious and can be transmitted, but the resulting cancer is not, as the malignancy is a consequence of the virus causing DNA changes in the host cells.
Primary Risk Factors and Causes
The vast majority of squamous cell carcinomas are directly attributable to cumulative exposure to ultraviolet (UV) radiation from sunlight and indoor tanning beds. UV rays penetrate the skin and cause direct damage to the DNA of keratinocytes, leading to the mutations that initiate cancerous growth. The risk is directly related to the total amount of sun exposure accumulated over a lifetime.
Other significant factors contributing to SCC development relate to chronic damage and a weakened immune response. Individuals who are immunosuppressed, such as organ transplant recipients taking anti-rejection medications, have a significantly higher risk of developing the disease. A suppressed immune system is less effective at detecting and eliminating damaged cells before they become malignant.
Chronic skin inflammation from conditions like long-standing scars, burns, or non-healing wounds can also create an environment conducive to SCC development. Exposure to certain environmental carcinogens, such as arsenic, or having a history of precancerous lesions like actinic keratoses substantially increases risk. The risk of developing SCC also increases noticeably with age, as the body’s natural cellular repair mechanisms become less efficient.