Basal and squamous cell cancers
Basal and squamous cell skin cancers are by far the most common cancers of the skin. Both are found mainly on parts of the body exposed to the sun, such as the head and neck. These cancers are strongly related to a person’s sun exposure.
Basal and squamous cell cancers are much less likely than melanomas to spread to other parts of the body and become life threatening. Still, it’s important to find and treat them early. If left alone, they can grow larger and invade nearby tissues and organs, causing scarring, deformity, or even loss of function in some parts of the body. Some of these cancers (especially squamous cell cancers) can spread if not treated, and in some cases they can even be fatal.
Melanomas are cancers that develop from melanocytes, the cells that make the brown pigment that gives skin its color. Melanocytes can also form benign (noncancerous) growths called moles. (Your doctor might call the mole anevus.)
Melanomas can occur anywhere on the body, but are more likely to start in certain areas. The trunk (chest and back) is the most common place in men. In women, the legs are the most common site. The neck and face are other common places for melanoma to start.
Melanomas are not as common as basal cell and squamous cell skin cancers, but they can be far more serious. Like basal cell and squamous cell cancers, melanoma is almost always curable in its early stages. But if left alone, melanoma is much more likely to spread to other parts of the body, where it can be very hard to treat.
Other skin cancers
There are many other types of skin cancers as well, but they are much less common:
Together, these types account for less than 1% of all skin cancers.
It’s important for doctors to tell the types of skin cancer apart, because they are treated differently. It’s also important for you to know what skin cancers look like. This can help you find them at the earliest possible stage, when they are cured most easily.
Once the type of melanoma has been established, the next step is to classify the disease as to its degree of severity.
Classifications for melanomas are called stages. The stage refers to the thickness, depth of penetration, and the degree to which the melanoma has spread. The staging is used to determine treatment.
Early melanomas (Stages 0 and I) are localized; Stage 0 tumors are in situ, meaning that they are noninvasive and have not penetrated below the surface of the skin, while Stage I tumors have invaded the skin but are small, nonulcerated, and are growing at a slow mitotic rate. Stage II tumors, though localized, are larger (generally over 1 mm. thick) and/or may be ulcerated or have a mitotic rate of greater than than 1/mm2; they are considered intermediate melanomas. More advanced melanomas (Stages III and IV) have spread (metastasized) to other parts of the body. There are also subdivisions within stages.