Your skin protects your body from
heat, injury, and infection. It also protects your body from
damage caused by ultraviolet (UV) radiation (such as from the sun
Your skin stores water and fat. It
helps control body heat. Also, your skin makes vitamin D.
The picture shows the two main
layers of the skin:
The epidermis is the top layer of your skin. It's mostly made of flat cells
called squamous cells.
Below the squamous cells deeper in the epidermis are round cells called basal
Cells called melanocytes are scattered among the
basal cells. They are in the deepest part of the epidermis. Melanocytes
make the pigment (color) found in skin. When skin is exposed to UV
radiation, melanocytes make more pigment, causing the skin to darken, or
The dermis is the layer under the epidermis. The dermis contains many
types of cells and structures, such as blood vessels, lymph
vessels, and glands. Some of these glands make
sweat, which helps cool your body. Other glands make sebum. Sebum is an
oily substance that helps keep your skin from drying out. Sweat and sebum
reach the surface of your skin through tiny openings called pores.
Skin cancers are named for the type
of cells that become malignant (cancer). The three most common types are:
Melanoma begins in melanocytes (pigment cells). Most melanocytes are in
Melanoma can occur on any skin surface. In men, it's often found on the
skin on the head, on the neck, or between the shoulders and the hips. In
women, it's often found on the skin on the lower legs or between the
shoulders and the hips.
Melanoma is rare in people with dark skin. When it does develop in people
with dark skin, it's usually found under the fingernails, under the
toenails, on the palms of the hands, or on the soles of the feet.
Basal cell skin cancer: Basal cell skin cancer begins in the basal cell layer
of the skin. It usually occurs in places that have been in the sun. For
example, the face is the most common place to find basal cell skin cancer.
with fair skin, basal cell skin cancer is the most common type of skin cancer.
Squamous cell skin cancer: Squamous cell skin cancer begins in squamous cells.
In people with dark skin, squamous cell skin cancer is the most common
type of skin cancer, and it's usually found in places that are not in the
sun, such as the legs or feet.
However, in people with fair skin, squamous cell skin cancer usually
occurs on parts of the skin that have been in the sun, such as the head,
face, ears, and neck.
Unlike moles, skin cancer can invade
the normal tissue nearby. Also, skin cancer can spread throughout the body.
Melanoma is more likely than other skin cancers to spread to other parts of the
body. Squamous cell skin cancer sometimes spreads to other parts of the body,
but basal cell skin cancer rarely does.
When skin cancer cells do spread,
they break away from the original growth and enter blood vessels or lymph
vessels. The cancer cells may be found in nearby lymph nodes. The cancer
cells can also spread to other tissues and attach there to form new tumors that
may damage those tissues.