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Know Your Skin

Skin is the body's largest organ. This page covers what skin cancer is, the three main types, the ABCDE rule for spotting suspicious moles, and how to perform a monthly skin self-check.

What skin cancer is

Skin cancer occurs when cells in the skin begin growing in an uncontrolled way. Those abnormal cells can invade and damage healthy tissue. The encouraging news: roughly 90% of skin cancers are preventable through sun-protective habits.

There are three main types to recognize.

The three main types

Knowing what each one looks like helps with early detection — when treatment is most effective.

1

Basal Cell Carcinoma

The most common form. Basal cells are responsible for producing new skin cells. This cancer typically appears as a raised bump, sometimes with visible small blood vessels. It can be pale, pink, or red.

Where it appears: Sun-exposed areas — face, neck, arms.

2

Squamous Cell Carcinoma

Affects the middle layer of the epidermis (the outer skin layer). It commonly appears as a red, scaly patch or a sore that does not heal.

Where it appears: Lips, ears, hands, and other frequently sun-exposed sites.

3

Melanoma

The most serious form. Melanoma begins in melanocytes — the pigment-producing cells. It typically appears as a changing mole or a new pigmented spot.

Where it appears: Anywhere on the body, including areas with minimal sun exposure.

Source: American Cancer Society

The ABCDE rule

A memory aid dermatologists use to evaluate moles. When checking your skin, look for these five characteristics:

A
Asymmetry

One half of the mole doesn't match the other half.

B
Border

The edges look uneven, ragged, blurry, or notched.

C
Color

More than one color (brown, black, pink, red, blue, white).

D
Diameter

Bigger than a pencil eraser (about 6 mm or ¼ inch).

E
Evolving

The mole is changing — in size, shape, color, or feeling.

If a mole shows any of the ABCDE warning signs, consult a dermatologist.

Monthly skin self-check

A quick monthly self-exam takes about five minutes. Younger children should do this with a parent. Pick a memorable date — the first Saturday of the month works well as a recurring cue.

  1. Use good lighting

    Stand in a well-lit area. A bathroom mirror with overhead light works well.

  2. Examine head to toe

    Check face, ears, scalp (part the hair to see clearly), neck, chest, abdomen, back, arms, hands, legs, and the tops and bottoms of the feet.

  3. Don't skip less-visible areas

    Between the toes, behind the ears, inside the mouth, and the soles of the feet. Skin cancer can develop anywhere — including areas that rarely see direct sun.

  4. Apply the ABCDE rule

    Flag any mole that is Asymmetric, has an irregular Border, multiple Colors, a Diameter greater than 6 mm, or is Evolving over time.

  5. Photograph spots to monitor

    Photos provide a baseline for month-to-month comparison. Subtle changes become easier to detect over time.

When to see a dermatologist

Schedule an appointment if you notice any of the following:

  • A mole changing in size, shape, or color
  • A new spot that persists
  • A sore that does not heal within a few weeks
  • A patch that itches, hurts, bleeds, or feels different from the surrounding skin

Early detection saves lives. Most skin cancers diagnosed early are highly treatable.