The majority of squamous cell carcinomas are caused by sun exposure. Ultraviolet (UV) radiation, which is generated by the sun (as well as tanning beds) can damage the cellular DNA in the outer layers of skin. Normally, new skin cells push older cells toward the skin’s surface, where they are ultimately shed. DNA damage can disrupt this process, causing skin cells to grow uncontrollably and accumulate into cancerous lesions.
While scientists have conclusively confirmed that UV exposure causes squamous cell carcinoma, this does not explain why skin cancer sometimes develops in areas of the body that are not usually exposed to sunlight, such as the buttocks, genitals, palms of the hands and soles of the feet. Instead, it suggests that other causes exist and have yet to be identified.
How can squamous cell carcinoma develop without UV exposure?
Like all types of cancer, squamous cell carcinoma is not triggered by a single cellular change. Rather, a series of changes is required. In addition to UV exposure, other factors may be involved, such as:
- Genetic predisposition – Sometimes, “cancer-causing” genes are passed from parent to child. In these cases, some of the changes needed to trigger squamous cell carcinoma are already present at birth.
- Environmental toxins – Chemical burns and exposure to certain pollutants, such as tobacco smoke, motor vehicle exhaust and arsenic (which may be found in soil, water and air) can cause skin damage that leads to squamous cell carcinoma.
- Immune system deficiencies – Immune-suppressing drugs taken after an organ transplant or certain viral infections, such as human papillomavirus (HPV) and human immunodeficiency virus (HIV), can weaken the immune system, making the body less effective at eliminating damaged skin cells.
Many people are aware of the importance of using sunscreen, but it’s essential to understand that the sun is not the only cause of skin cancer. Therefore, any unusual skin changes – regardless of where on the body they occur – should be promptly discussed with a physician.
If you’d like to consult with a skin cancer specialist in the Cutaneous Oncology Program at Moffitt Cancer Center, you can request an appointment by calling 1-888-663-3488 or completing our new patient registration form online. Referrals are welcome but not required.