Squamous cell carcinoma is a common type of skin cancer that occurs when cells in the top layer of skin (the epidermis) grow out of control. Squamous cells are flat cells in the upper (outer) part of the epidermis that constantly shed as new cells form.
About 20% of all skin cancers are squamous cell carcinomas. Squamous cell carcinoma often develops on sun-exposed areas of the body such as the face, lips, ears, scalp, neck, shoulders, backs of the hands, and forearms, though it can develop anywhere on the skin.
Squamous cell carcinoma is usually a slow-growing cancer. It rarely metastasizes (spreads), and most cases of squamous cell carcinoma are diagnosed before the cancer has progressed beyond the upper layer of skin.
What Are Symptoms of Squamous Cell Carcinoma?
Characteristics of squamous cell carcinomas include:
What Causes Squamous Cell Carcinoma?
Most squamous cell carcinomas are caused by repeated unprotected skin exposure to ultraviolet (UV) light from sunlight and tanning beds.
Risk factors for developing squamous cell carcinoma include:
- Ultraviolet (UV) light exposure (sunlight and tanning beds)
- Light-colored skin
- Being male
- Older age
- Previous skin cancer
- Radiation treatment
- Smoking
- Exposure to certain chemicals such as arsenic, coal tar, paraffin, and some petroleum products
- Psoriasis treatment with psoralens and ultraviolet light (PUVA)
- Long-term or severe skin inflammation or injury
- Scars from severe burns, areas of skin over serious bone infections, and skin damaged by severe inflammatory skin diseases
- Xeroderma pigmentosum
- Basal cell nevus syndrome (also called nevoid basal cell carcinoma syndrome or Gorlin syndrome)
- Weakened immune system from certain diseases or medical treatments
How Is Squamous Cell Carcinoma Diagnosed?
Squamous cell carcinoma is diagnosed with a patient history and physical examination of the skin, along with tests such as:
- Skin biopsy
- Lymph node biopsy
- Imaging tests (used if cancer is suspected to have spread deeply below the skin or to other parts of the body)
- Computerized tomography (CT) scan
- Magnetic resonance imaging (MRI) scan
What Is the Treatment for Squamous Cell Carcinoma?
Treatment for squamous cell carcinoma may include one or more of the following:
- Surgery
- Excision
- Curettage and electrodesiccation
- Mohs surgery (also called Mohs micrographic surgery, or MMS)
- Lymph node surgery
- Skin grafting and reconstructive surgery
- Local treatments
- Cryotherapy
- Photodynamic therapy (PDT)
- Topical chemotherapy
- 5-fluorouracil (5-FU) (Efudex, Carac, and Fluoroplex)
- Immune response modifiers
- Interferon
- Laser surgery
- Radiation therapy
- Used when a tumor is very large or is on an area of the skin where it is difficult to remove with surgery
- Can often cure small squamous cell skin carcinomas and can delay the growth of advanced cancers
- Systemic chemotherapy
- Cisplatin
- 5-fluorouracil (5-FU)
- Targeted therapy
- Hedgehog pathway inhibitors: vismodegib (Erivedge) and sonidegib (Odomzo)
- EGFR inhibitors: cetuximab (Erbitux)
- Immunotherapy for advanced squamous cell skin cancers
- Immune checkpoint inhibitors called PD-1 inhibitors: cemiplimab (Libtayo) and pembrolizumab (Keytruda)
From 
https://www.cancer.org/cancer/basal-and-squamous-cell-skin-cancer.html
https://www.skincancer.org/blog/how-serious-is-a-squamous-cell-carcinoma/
https://moffitt.org/cancers/squamous-cell-carcinoma/