Squamous Cell Carcinoma
Squamous Cell Carcinoma is the second most common type of skin cancer that is caused by ultraviolet rays (sunshine), arsenic ingestion, some wart viruses (human papilloma virus), and radiation.
Invasive Squamous Cell Carcinoma
Although uncommon, this tumor does have the potential to metastasize (spread to the lymph nodes and internal organs) and can be fatal. In general, this risk is very low and estimated to be approximately 3%. Tumors that occur within a burn scar and those that are on the lip or ear are more likely to metastasize than those elsewhere and carry a risk of up to 15%.
In most cases, surgery (Mohs' micrographic surgery, excision, or electrodessication and curettage) or radiation is used to treat these tumors. There are pros and cons to each treatment method with differences in cure rate, healing time, post-treatment restrictions, and cosmetic outcome.
Squamous Cell Carcinoma in situ (non-invasive)
Early, non-invasive tumors are called squamous cell carcinoma in-situ (or intraepithelial squamous cell carcinoma or Bowen’s disease), which does not pose a metastasis risk at this early stage. Tumor cells are present only in the epidermis, the top layer of skin, where there are no blood vessels and therefore no risk of spreading. This early variant is not life-threatening unless untreated, in which case it can become invasive with time (months to years).