Squamous cell carcinoma (SCC) is the second most common skin cancer (basal cell carcinoma is the most common). While basal cell carcinoma (BCC) rarely spreads to internal organs, SCC can spread to lymph nodes and internal organs.
What causes SCC?
Much like basal cell carcinoma, SCC is associated with ultraviolet light damage. It is much more common in fair-skinned individuals than those with pigmented skin. Other forms of radiation damage (e.g. X-rays) are also associated with SCC. Some industrial chemicals have been associated with SCC, as has human papilloma virus (HPV). Those with suppressed immune systems are also much more susceptible to SCC. Such patients include organ transplant recipients and those with certain forms of leukemia.
How do I know if my SCC is serious?
All SCC have the potential to spread internally, but there are certain high-risk features including:
- Large size (more than 2.0 cm wide on the body or 1.0cm wide on the face)
- A deep tumor (more than 4-6mm deep)
- Certain body locations (lip, ears, hands)
- A tumor that was previously removed and recurred
- Rapid growth
- Certain findings on the pathology report (perineural invasion, poor differentiation)
- Symptoms such as numbness or pain
Sometimes, for very concerning tumors, a provider may wish to order imaging (e.g. CT scan, MRI) or sample nearby lymph nodes (AKA sentinel node biopsy).
Are there different types of SCC?
Yes, there two broad groups of SCC:
- SCC in situ. This is SCC that is confined to the epidermis (top layer of skin). SCC in situ is sometimes called Bowen's disease.
- Invasive SCC. Here, the SCC has broken past the barrier between epidermis and is extending into the dermis (the thicker and deeper layer or skin). For invasive SCC, there can be other features that help distinguish tumors. Differentiation refers to how "normal" or "abnormal" the cells appear under the microscope. Well-differentiated tumors (relatively "normal" appearing) are, in general, less concerning than poorly differentiated tumors ("abnormal" appearing). Another feature of importance is the term perineural. This means that the tumor has gotten into one or more nerves. Once in a nerve, this situation creates a simple and rapid means for the tumor to spread, which is very risky. There is a myriad of other terms that can be included in the pathology report, meaning that the provider reading the report must be trained in both pathology and management of these tumors.
How can my SCC be treated?
There are topical (cream), surgical, radiation and drugs that can treat SCC. SCC in situ can often be treated with a topical cream such as 5-fluorouracil or imiquimod with good success and careful follow-up.
Surgical excision can include traditional excision with post-operative margin assessment or Mohs micrographic surgery. Traditional excision involves removing the tumor with a margin of normal-appearing skin, closing the wound and sending the tissue to a pathology laboratory to check that the outside of the specimen (margins) are free of tumor.
Mohs micrographic surgery involves removing the tumor with a smaller margin of normal-appearing skin and checking the margins of the specimen under the microscope prior to closing the wound. After clearing the tumor (usually within 1-2 hours), the wound can be reconstructed.
Reconstructive options for skin cancer depend on the location and size of the wound as well as the quality of the skin. Small and shallow wounds can be allowed to heal on their own (second intent healing). Deeper wounds are usually brought together in a linear closure. Some wounds, however, cannot be brought together because there is no adequate skin laxity. In these cases, a flap or graft may be required (How Will My Surgeon Repair My Wound?). The SUTUREGARD ISR Device can be used to relax many wounds that would otherwise require flaps or grafts.
For more aggressive cancers, radiation therapy can be used to deliver very intense energy to destroy the cancer. Unfortunately, normal tissue and blood supply can also be adversely affected. New drug treatments (e.g. Cemiplimab) are also available and very promising for advanced SCC. For some tumors, a combination of treatments may be required.
After successful treatment of the SCC, it is important to follow up with a provider who is experienced in skin cancer surveillance. A good example would be a member of the American Academy of Dermatology (AAD) (www.aad.org).