Melanoma (cont.)
Understanding cancer
Cancer begins in cells, the building blocks that make up tissues. Tissues
make up the organs of the body. Normally, cells grow and divide to form new
cells as the body needs them. When cells grow old, they die, and new cells take
their place.
Sometimes this orderly process goes wrong. New cells form when the body does
not need them, and old cells do not die when they should. These extra cells can
form a mass of tissue called a growth or tumor. Not all tumors are cancer.
Tumors can be benign or malignant:
- Benign tumors are not cancer:
- They are rarely life threatening.
- Usually, benign tumors can be removed, and they seldom grow back.
- Cells from benign tumors do not spread to tissues around them or to other
parts of the body.
- Malignant tumors are cancer:
- They are generally more serious and may be life threatening.
- Malignant tumors usually can be removed, but they can grow back.
- Cells from malignant tumors can invade and damage nearby tissues and organs.
Also, cancer cells can break away from a malignant tumor and enter the
bloodstream or lymphatic system. That is how cancer cells spread from the
original cancer (the primary tumor) to form new tumors in other organs. The
spread of cancer is called metastasis. Different types of cancer tend to spread
to different parts of the body.
Melanoma
Melanoma occurs when melanocytes (pigment cells) become malignant. Most
pigment cells are in the skin; when melanoma starts in the skin, the disease
is called cutaneous melanoma. Melanoma may also occur in the eye (ocular
melanoma or intraocular melanoma). Rarely, melanoma may arise in the
meninges, the digestive tract, lymph nodes, or other areas where melanocytes
are found. Melanomas that begin in areas other than the skin are not
discussed in this booklet. The Cancer Information Service (1-800-4-CANCER)
can provide information about these types of melanoma.
Melanoma is one of the most common cancers. The chance of developing it
increases with age, but this disease affects people of all ages. It can occur on
any skin surface. In men, melanoma is often found on the trunk (the area between
the shoulders and the hips) or the head and neck. In women, it often develops on
the lower legs. Melanoma is rare in black people and others with dark skin. When
it does develop in dark-skinned people, it tends to occur under the fingernails
or toenails, or on the palms or soles.
When melanoma spreads, cancer cells may show up in nearby lymph nodes.
Groups of lymph nodes are found throughout the body. Lymph nodes trap
bacteria, cancer cells, or other harmful substances that may be in the
lymphatic system. If the cancer has reached the lymph nodes, it may mean
that cancer cells have spread to other parts of the body such as the liver,
lungs, or brain. In such cases, the cancer cells in the new tumor are still
melanoma cells, and the disease is called metastatic melanoma, not liver,
lung, or brain cancer.
Next: What are risk factors for melanoma? »
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