Skin cancer is the most common human cancer. It is thought to be more common than all other cancer types combined. The majority of skin cancers are caused by sun exposure, sun burns, and/or tanning bed exposure, typically years prior to the development of the cancer. However, skin cancer can develop in any site, including those typically protected from the sun, so it is important to have full body skin checks for complete skin cancer screening.
There are three main types of skin cancer: basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and melanoma. Sometimes, BCCs and SCCs are lumped together into a category called non-melanoma skin cancers (NMSCs). NMSC is usually but not always less aggressive than melanoma.
Basal cell carcinoma (BCC) is the most common of the three types. While generally less aggressive than the other two types, basal cell skin cancers can destroy local tissue and in extremely rare cases, spread to the lymph nodes and elsewhere in the body. Depending on the location, size, and subtype (the way the cancer cells look under the microscope) of your basal cell, options for treatment may include Mohs micrographic surgery, standard excision (also known as wide local excision), electrodessication and curettage (also known as an ED&C, or the “scrape and burn” technique), or topical chemotherapy creams.
I think of squamous cell carcinoma (SCC) as the intermediate skin cancer, both in terms of how aggressive it is and how common it is. Many squamous cell skin cancers are slow-growing and easily treatable; however, up to 5% can have serious complications, including recurrence after treatment, spread to the lymph nodes or elsewhere in the body, and even death. For this reason, SCC must be taken very seriously. In general, topical treatments, such as ED&C and chemotherapy creams are less useful for SCC, and standard excision or Mohs micrographic surgery are better options in order to ensure complete removal and reduce the risk of complications. Some squamous cell carcinomas are confined to the top layer of the skin only and are called squamous cell carcinoma in situ (SCCIS). These are early stage SCCs and have a wide range of treatment options similar to those used for BCCs.
Melanoma is the least common but most aggressive of the three types of skin cancer. Melanomas carry the highest risk for metastasis to other sites in the body and death related to skin cancer. The risk for a particular melanoma relates directly to how deep the cancer cells are found in the skin, measured in millimeters. Dermatologists and dermatologic surgeons like myself treat lower-risk melanomas, which are defined as either melanomas in situ (MIS) or T1a melanomas (less than 0.8mm in depth without ulceration). These relatively superficial melanomas are almost always treated surgically, either with wide local excision or something called “slow Mohs,” a procedure done over several days in which tissue is removed and examined under the microscope prior to sewing the area closed. This process may take up to a week and may have to be repeated to remove all the cancer. If you have a deeper melanoma, you will likely be referred to a surgical oncologist, a type of surgeon who specializes in a procedure called a sentinel lymph node biopsy, which allows the lymph nodes to be checked for melanoma cancer cells at the same time as the removal of the skin cancer.
Frequently Asked Questions
Yes. Skin cancers most often have roots that are not entirely removed by the biopsy. Even if the margins are reported as clear on a small biopsy, this is does not guarantee that the cancer is entirely gone.
In general, no. While there are rare “overlap” cancers that share features of more than one type of skin cancer, a basal cell carcinoma, for example, will always be a basal cell carcinoma, but it will eventually become larger if not treated.
Although Mohs surgery has the highest cure rates and removes the least amount of tissue when compared to other forms of skin cancer treatment, it is not used for every skin cancer. It would be “overkill,” for example, to use Mohs surgery for a small basal cell skin cancer on the arm. In 2012, a group of physicians came together to develop Mohs “appropriate use criteria,” which classify which skin cancers are appropriate for Mohs surgery. It is widely followed and how I generally determine if a particular skin cancer will benefit from Mohs. In general, most skin cancers on the scalp, face, neck, hands, genitals, shins, and feet qualify, as do large or aggressive skin cancers elsewhere on the body. Most small skin cancers on the trunk or arms/legs do not qualify and are more appropriately treated with excision, ED&C, or topical chemotherapy creams.
After getting a first skin cancer, the odds of developing a second one at a new site is approximately 50% over the next five years. So, the answer is—maybe. Additionally, even after appropriate treatment, there is always a very low but real risk of recurrence of a previously treated skin cancer. This is why it is extremely important to undergo regular full body skin examinations at an interval recommended by your doctor after one has developed a skin cancer.
- Sun protection: this includes staying out of the sun whenever possible, wearing sunscreen (SPF greater than 30) when in the sun (including while driving) and re-applying often, using sun-protective clothing, and never using tanning beds.
- Follow-up skin checks: these may range from every 3 months to once a year depending on the type and number of previous skin cancers that you have had.
- Self skin examinations: every month, you and/or a partner should check your entire body for any new or changing spots and notify your dermatologist ASAP if you notice anything concerning.
- Nicotinamide: this is an over-the-counter vitamin supplement (related to Vitamin B3) that may reduce the risk of skin cancers and pre-cancers. Check with your doctor before starting nicotinamide.
- A healthy diet, high in fiber: while data are very preliminary, there is some early evidence that healthy diets high in fiber boost the body’s immune system through an effect on the gut microbiome (the healthy bacteria that live in the gut). And regardless, a healthy diet and high-fiber foods have many other health benefits besides possibly reducing the risk of skin cancer.
Skin cancer cure rates vary widely depending on the type of skin cancer and the method by which it was treated. Cure rates may be as high as 99% when Mohs micrographic surgery is used for small low-risk cancers, meaning only a 1% (1 in 100) chance of the cancer coming back. However, for larger or more complex skin cancers (such as ones that were previously treated and have come back or ones that have a concerning appearance under the microscope), cure rates are lower and thus recurrence rates are higher. Depending on the type of treatment and the specifics of your skin cancer, cure rates range from 80-98%, meaning that the risk of the skin cancer coming back ranges from 1 in 50 (2%) to as high as 1 in 5 (20%) in certain situations. This highlights the importance of regular full body skin examinations, during which the dermatologist will check the entire body surface, paying special attention to any scars at sites of previous skin cancer removal(s).