Moles & Benign Lesions
These appear during childhood or adulthood. There are 3 types of acquired nevi.
Junctional Melanocytic Nevi
- They tend to first appear in childhood as flat, freckle-like lesions of brown, dark brown, or black, and are uniform in color.
- These moles are called “junctional nevi” because the melanocytes that make them are located at the junction of the epidermis and dermis.
- They are most commonly found on the face, arms, legs, trunk, genitals, or soles of the feet.
- During adulthood, these nevi may become more raised, lose pigmentation, or even disappear.
- These are flesh-colored or light brown, dome-shaped lesions that are only on the dermis.
- The other name for these moles are “dermal nevi”.
- The melanocytes that make up an intradermal nevus are located in the dermis (below the dermo-epidermal junction). This mass of melanocytes pushes the cells above it upward, resulting in the flesh-colored bump that is noted on the surface of the skin.
- They are most commonly found in adults.
- Nonpigmented dermal nevi are also called cellular nevi.
- These have features of both junctional and intradermal nevi.
- The melanocytes are located both in the dermo-epidermal junction and the dermis. They are usually raised and have uniform pigmentation.
Other Benign Lesions
- Small, tan, flat spots that appear in response to the sun’s ultraviolet radiation.
- The medical name for a freckle is an “ephelide”.
- Freckles darken with sun exposure and lighten or fade when no longer exposed.
- They tend to cluster together in large numbers.
Lentigines (singular, lentigo)
- Also known as sunspots, age spots, or liver spots, although they have nothing to do with the liver or liver function. Lentigines are flat, brown, sometimes large spots that are associated with sun-damaged skin.
- Unlike freckles, they are usually discrete spots that do not fade when no longer exposed to the sun.
- Lentigines are very common in people over 40.
- You’ll find them in areas of greatest sun exposure: on the face, arms, chest, shoulders, back, and backs of the hands.
- IMPORTANT! Because lentigines are a marker for sun damage, people with lentigines are at increased risk for developing melanoma.
- Raised, benign growths of keratinocytes in the upper layers of the skin (the epidermis). These keratinocytes are often pigmented, which gives the seborrheic keratosis its dark, mole-like appearance.
- They are sometimes mistaken for warts or melanoma and range in color from tan to dark brown or black. They have a waxy, pasted-on appearance which is why they are sometimes described as “brown candle wax on the skin.”
- Seborrheic keratoses can appear on sun-exposed or covered areas. They never grow on the palms or soles or in the mouth or eyes.
- Unlike moles, seborrheic keratoses are usually rough to the touch.
- Seborrheic keratoses are the most common benign lesions that mimic the appearance of melanoma. Although a seborrheic keratosis cannot turn into a melanoma because it is not made of melanocytes, it cannot be completely ignored because a melanoma can occur next to them and may be mistaken for an extension of the seborrheic keratosis.
Layers of the Skin
The First Layer: Epidermis
The thin top layer of skin we can see with the naked eye.
A waterproof barrier that protects us from bacteria and other microscopic organisms in the environment.
Cells within the epidermis:
- Keratinocytes are specialized skin cells that make up most of the epidermis. The outermost part of the epidermis is made up of keratinocytes that have lost their nucleus, are full of a protein called keratin that makes them hard, and link together to form a waterproof barrier. Keratinocytes are constantly shed and replaced by squamous cells that turn into keratinocytes as they migrate up to the top of the skin.
- Squamous cells are live keratinocytes that make keratin, an important skin protein.
- Basal cells make up most of the basal layer, the innermost layer of the epidermis. They are the only cells in the epidermis that divide and create new cells called keratinocytes.
- Melanocytes are located in the basal layer of the epidermis. They are interspersed regularly between the basal cells. Melanocytes produce melanin, a pigmented protein that gives us our skin and hair color and provides protection against the damaging effects of ultraviolet radiation.
The Second Layer: Dermis
The thicker, second layer of skin located beneath the epidermis. Contains blood and lymph vessels, nerve endings, muscle fibers, oil and sweat glands, and hair follicles
There are 2 layers within the Dermis:
- Papillary dermis, the upper layer
- Made of loose connective tissue, blood vessels, and nerves. Fingerlike projections called papillae connect the dermis to the epidermis and provide the epidermis with vital nutrients.
- Reticular dermis, the thicker lower layer
- A network of collagen fibers, dense connective tissue that gives skin its elasticity and strength
- Contains a rich supply of blood vessels and nerves, as well as lymph vessels, glands, and hair follicles
The Bottom Layer: Subcutaneous Layer or Subcutis
A thick layer of fat and connective tissue beneath the dermis
- Like the dermis, it contains a rich supply of blood and lymph vessels.
- It insulates and saves your body heat, acts as a shock absorber to protect your underlying tissues and organs from injury, and is a source of reserve energy.
Melanocytes and Melanin
Melanocytes are cells located in the lower part of the epidermis, just above the dermis. They make the pigment called melanin, which gives color to the skin, hair, and parts of the eye.
Melanin protects the skin from ultraviolet (UV) radiation, the harmful rays of the sun.
A mole is a cluster of melanocytes that appears as a pigmented spot on the skin.
- Moles can be either flat or raised, round or oval, and are usually smaller than a pencil eraser.
- Although generally benign and unchanging, moles can sometimes become cancerous.
- The first sign of melanoma is often a change in the size, shape, or color of an existing mole or the appearance of a new mole in adulthood. (See Moles and Other Lesions for more information.)
Both light- and dark-skinned people have the same number of melanocytes. The differences in skin color are the result of differences in the amount of melanin and the size of the melanin “packets” that each melanocyte makes.
- Eumelanin is a red-yellow pigment most often found in fair-skinned people with red hair. Some red-haired people appear to not have any moles, because theirs are pink to red, not brown.
- People with more eumelanin are more likely to tan and to
be protected from UV radiation.
- People with less eumelanin are more likely to freckle or burn.
- People with more eumelanin are more likely to tan and to
- Pheomelanin, the most plentiful of human melanin, is found in brown and black skin and hair.
- Albinos are unable to produce normal quantities of melanin and so have reduced levels or an absence of pigment in their skin, hair, and eyes.
Moles & Other Lesions
Moles are pigmented spots on the skin formed from clusters of melanocytes. Moles may be acquired or congenital.
- Acquired nevi appear during childhood or adulthood
- Congenital nevi are present at birth
Some skin lesions may resemble melanoma but are in actuality noncancerous growths. When you see new growths, or old ones start to change, it’s time to look at them more closely. By becoming familiar with your own skin lesions, you will be better able to tell those that are normal growths and those that need to be seen by your doctor.
- Definition: The medical term for a mole is melanocytic nevus. The term “nevus” is a medical term that means a collection of the same kind of cell. A melanocytic nevus, as the name suggests, means a collection of melanocytes. Because melanocytic nevi are by far the most common nevi seen or examined, doctors will often drop the word “melanocytic” and just refer to them as “nevus”. The word “nevus” is the Latin word for “birthmark”.
- Shape: Moles may be flat or raised, round or oval, and are smaller than 6 millimeters, or 1/4 inch, in diameter, like the width of a pencil eraser. The borders are usually smooth and have a defined outline.
- Color: Moles can be pink flesh tones to dark brown or black. Ordinary moles are usually a uniform brown, tan, or flesh-colored spot.
- Number of moles: This is determined by one’s genes and is based on the amount of sun exposure.
Changes in Moles
- The first sign of melanoma is sometimes a change in the size, shape, or color of an existing mole or the appearance of a new mole.
- Usually, moles don’t change in size, shape, and color from year to year.
- Even though most people think that melanomas arise from pre-existing moles, many melanomas arise in “normal” skin, where there was no previous mole.
- If you notice changes in a mole or a new mole, contact your doctor for a medical evaluation.
- Moles may emerge anywhere on the skin, either singly or in groups. Several moles may appear on the skin at the same time, especially in areas that have been exposed to the sun. Moles may darken following sun exposure or during pregnancy.
- During adulthood, they often lose their pigmentation, and they may even seem to disappear in old age. Most moles will follow a pattern of aging over the course of an individual’s life. As moles “age” they commonly will slowly “raise up” so they can be felt, and over years to decades very slowly lose their color. They eventually become very soft and turn the same color as the rest of the skin. For this reason, some elderly appear to have no moles, when in fact their moles have gone through this normal life cycle called “senescence”, and are not noticeable unless one looks carefully.
- Remember, these normal changes occur VERY slowly, while changes in moles that make one concerned about possible melanoma occur quickly; in the order of weeks to months.
- If you ever have a question about a change in a mole, do not brush it off. Always see a physician who can look at it with you.