Once keratinocytes begin to grow uncontrollably, they have the potential to become cancerous and produce squamous cell carcinoma. The lesion caused by SCC is often asymptomatic
Ulcer or reddish skin plaque that is slow growing
Intermittent bleeding from the tumor, especially on the lip
The clinical appearance is highly variable
Usually the tumor presents as an ulcerated lesion with hard, raised edges
The tumor may be in the form of a hard plaque or a papule, often with an opalescent quality, with tiny blood vessels
The tumor can lie below the level of the surrounding skin, and eventually ulcerates and invades the underlying tissue
The tumor commonly presents on sun-exposed areas (e.g. back of the hand, scalp, lip, and superior surface of pinna)
On the lip, the tumor forms a small ulcer, which fails to heal and bleeds intermittently
Evidence of chronic skin photodamage, as in multiple actinic keratoses (solar keratoses)
The tumor grows relatively slowly

Spread
Unlike basal-cell carcinoma (BCC), squamous cell carcinoma (SCC) has a higher risk of metastasis. Risk of metastasis is higher clinically in SCC arising in scars, on the lower lips or mucosa, and occurring in immunosuppressed and solid organ transplant patients. Risk of metastasis is also higher in SCC that are >2 cm in diameter, growth into the fat layer and along nerves, thickness >6mm. Causes
Squamous cell carcinoma is the second-most common cancer of the skin (after basal-cell carcinoma but more common than melanoma). It usually occurs in areas exposed to the sun.
Squamous-cell skin cancer, also known as cutaneous squamous-cell carcinoma (cSCC), is one of the main types of skin cancer along with basal cell cancer and melanoma. It usually presents as a hard lump with a scaly top but can also form an ulcer. Onset is often over months. Squamous-cell skin cancer is more likely to spread to distant areas than basal cell cancer. When confined to the outermost layer of the skin, a precancerous or in situ form of cSCC is known as Bowens disease.The greatest risk factor is high total exposure to ultraviolet radiation from the sun. Other risks include prior scars, chronic wounds, actinic keratosis, lighter skin, Bowens disease, arsenic exposure, radiation therapy, tobacco smoking, poor immune system function, previous basal cell carcinoma, and HPV infection. Risk from UV radiation is related to total exposure, rather than early exposure. Tanning beds are becoming another common source of ultraviolet radiation. Risk is also elevated in certain genetic skin disorders, such as xeroderma pigmentosum and certain forms of epidermolysis bullosa. It begins from squamous cells found within the skin. Diagnosis is often based on skin examination and confirmed by tissue biopsy.New in vivo and in vitro studies have proven that the upregulation of FGFR2, a subset of the fibroblast growth factor receptor (FGFR) immunoglobin family, has a critical role to play in the progression of cSCC cells. Mutation in the TPL2 gene causes overexpression of FGFR2, which activates mTORC1 and AKT pathways in both primary and metastatic cSCC cell lines.