NCCN Guidelines for Patients
Melanoma, Version 1.2014
How melanoma spreads
Melanoma skin tumors are made of abnormal
pigment cells (melanocytes) that have become cancer
See Figure 3.
These tumors are often brown or
black because the cells still make melanin. Melanoma
is more dangerous than most other common skin
cancers because it is more likely to spread if it isn’t
found early. However, most melanomas—about 90
out of 100—are found early before they have spread.
Melanoma has the potential to spread through the
dermis to nearby tissues and other parts of the body.
The deeper a melanoma grows into the dermis,
the higher the risk of spreading. This is why finding
melanoma as early as possible is so important. Most
people can be cured if melanoma is found early.
How melanoma spreads
Unlike normal cells, cancer cells can spread to other
parts of the body. This process is called metastasis.
The uncontrolled growth and spread of cancer cells
makes cancer dangerous. Cancer cells can replace or
deform normal tissue causing organs to stop working.
Cancer cells often spread to nearby and distant sites
through lymph or blood. Lymph is a clear fluid that
gives cells water and food. Lymph leaks out of blood
vessels and then flows through tiny tubes called
lymph vessels mostly in one direction toward the
heart, where lymph re-enters the blood. Lymph also
has white blood cells that fight germs. A lymph node
is a small group of special disease-fighting cells.
Lymph nodes filter lymph and remove germs. Lymph
nodes are connected to each other by lymph vessels.
Lymph vessels and nodes are found throughout the
See Figure 4.
Once melanoma has grown
into the dermis, it can reach the lymph vessels. The
melanoma cells can then travel through the lymph
vessels to the lymph nodes and other parts of the
Figure 3. Melanocytes of the epidermis
Melanocytes are located at the bottom of
the epidermis. These cells make melanin,
which spreads to the top of the epidermis
and gives skin its color. Melanoma tumors
are made of abnormal melanocytes that
have become cancer cells.
Derivative work of Anatomy: The Skin by Don Bliss available at: