NCCN Guidelines for Patients
Part 1: About melanoma
1.1 Layers of the skin
The skin is the largest organ of the body. It covers the
body’s entire surface. The skin has two layers (Figure
1). The outer layer, which can be seen, is called the
epidermis. Under the epidermis is the second layer,
called the dermis.
The main job of the epidermis is to protect the body and
help control body temperature. It is made up of four types
of cells, including melanocytes.
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. People with darker
skin have the same number of melanocytes as people
with lighter skin. The darkness of skin is based on how
much melanin is made by the melanocytes. Higher levels
of melanin cause the skin to be darker.
The dermis is much thicker than the epidermis. It
contains hair roots, glands, and nerve endings. Blood
and lymph vessels bring nutrients to the dermis and
epidermis. Connective tissue holds all these structures in
place and allows the skin to stretch.
Under the dermis is the hypodermis. It is mostly made
of fat and connective tissue. It is not part of the skin but
connects the skin to muscles and bones. It also saves
body heat, stores energy, and absorbs shock to protect
the body from injury. The fat and other tissues in the
hypodermis are also called “subcutaneous” tissues,
which means “below the skin.”
Figure 1. Parts of the skin
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