Non-Melanoma Skin Cancer
What are NMSCs? Non-melanoma skin cancers are the most common skin
cancers. They arise from skin cells in the epidermis, the outer-most layer of
the skin. The two most common NMSCs are basal cell carcinoma (BCC) and squamous
cell carcinoma (SCC). BCC is the most common human cancer and accounts for 80%
of all skin cancers. SCCs make up 16% of all skin cancers. BCCs and SCCs arise
from keratinocytes, the cells that make up most of the epidermis. There are two
main kinds of keratinocytes: basal cells that form the basal layer, and squamous
cells that lie just above the basal layer. BCCs arise from basal keratinocytes,
and SCCs develop from squamous keratinocytes.
Who gets NMSCs? NMSCs are most common on skin that has been exposed to a
lot of ultraviolet (UV) radiation over time, either from natural sunlight or
from tanning booths or phototherapy. There may be many years, or decades,
between the time of significant UV exposure and the development of NMSCS. NMSCs
are more commonly seen in individuals with fair skin, since they are more
susceptible to UV-induced skin damage, however NMSCs can occur in people of all
skin types and ethnic backgrounds. People with inherited genetic disorders (such
as xeroderma pigmentosum or basal cell nevus syndrome), immune suppression (such
as following a solid organ transplant), or who have been exposed to ionizing
radiation (such as X-ray treatment for certain kinds of cancer) may also be at
higher risk for developing NMSCs.
What do NMSCs look like? When they first appear, BCCs often look like pink
bumps resembling "pimples" except that they don't go away. Over time, they may
develop small dilated blood vessels on their surface ("spider veins"), and the
center of the growth may repeatedly break open and scab. Other types of BCC may
look like flat, pale pink, shiny "scars", sometimes with a slightly scaly
surface. BCCs typically grow quite slowly. It is very rare for BCC to
metastasize (spread to other parts of the body), therefore it is rare for BCC to
be life-threatening. However, untreated BCCs will continue to enlarge and invade
more deeply into the skin, and the results can be extremely disfiguring.
Compared to BCCs, SCCs may grow rapidly, and they often look like a large pink
"wart" that is firm and tender to the touch. SCCs tend to have more scale than
BCCs, and they sometimes have a central "crater" filled with firm, scaly
material. Some SCCs arise from a preexisting actinic keratosis. Occasionally,
SCCs develop from a non-healing "sore" such as a leg ulcer or from an old scar
(especially a burn scar). SCCs are more likely to metastasize than BCCs,
especially if they are located in high-risk areas such as the lip or ear. People
whose immune systems are not functioning properly (such as solid organ
transplant patients, the very elderly, or those with alcoholism) are also at
higher risk for metastasis.
How are NMSCs treated? There are many different ways to treat NMSCs.
Treatment options include destructions, chemotherapy, and surgery. Destructions
are procedures designed to physically remove the NMSC by cutting, scraping,
lasering, cauterizing ("burning"), or freezing with liquid nitrogen. A common
destruction used to treat NMSCs is called electrodesiccation and curettage
(ED&C), which is essentially a "burning and scraping" procedure. Topical
chemotherapy, using drugs applied to the skin to remove the cancerous cells, can
be used alone or together with destructions (especially ED&C). Surgery means
cutting the NMSC out of the skin, either by way of a standard excision or Mohs
micrographic surgery. The latter procedure, named after Dr. Frederick Mohs, is a
highly specialized surgical technique that is indicated for tumors located in
cosmetically sensitive areas (such as the nose, eyelid, lip, rim of ear), very
large tumors, tumors with ill-defined margins, tumors with an aggressive
microscopic appearance, or recurrent tumors.
Which treatment for NMSC is best? Which treatment option is best for each
situation depends on many factors, including the tumor's size, location,
microscopic appearance, as well as the age and general health of the patient and
the ultimate cosmetic outcome of the procedure. Your dermatology health care
provider can help you decide which treatment is most appropriate for each
particular situation.
How can NMSCs be prevented? The risk of NMSC can be decreased by
protecting the skin from excessive amounts of UV exposure. A combination
approach to sun protection is most effective. Avoid prolonged time in the sun
during the middle of the day (10am – 4pm), when the sun's rays are most intense.
Seek shade when possible. Wear protective clothing to shield the skin, including
hats and sunglasses. Apply sunscreen with at least SPF 15 twenty minutes before
exposing skin to UV light, and reapply it every ninety minutes if you get wet,
perspire a lot, or wipe off the skin. It takes one ounce of sunscreen to cover
an average-sized adult from head to toe. Remember that UV light passes through
clouds and window glass, so don't ignore sun protection on cloudy days or when
traveling in vehicles. If patients have already had one NMSC, they are at higher
risk for developing another, even if they are very careful about sun protection
on an ongoing basis in the future. However, it is still important that they
continue to practice careful sun protection measures. People cannot go back in
time and undo the UV damage that has already occurred to their skin, but they
can help prevent additional damage, which in turn may reduce their risk of
future skin cancers.
Elizabeth S. Miller, M.D., FAAD, FAAP