ABCDEs of Melanoma: How Doctors Diagnose Skin Cancer

Medically Reviewed By Raechele Cochran Gathers, MD
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The ABCDEs of melanoma outline five visible skin features that are characteristic of early melanoma. Dermatologists created the ABCDEs of melanoma to help people recognize the disease and catch it before it spreads. The American Academy of Dermatology estimates that 1 in 5 people in the United States will develop skin cancer in their lifetime. The ABCDEs of melanoma can help you catch skin cancer early enough to treat it effectively.

This article explains the ABCDEs of melanoma and how to check your skin for skin cancer, including tips for detecting cancer early. It also discusses different types of skin cancer, signs and symptoms, and when to call the doctor.

What are the ABCDEs of skin cancer?

Doctors use the ABCDE characteristics of skin damage to diagnose and classify skin cancer.
Doctors use the ABCDE characteristics of skin damage to diagnose and classify skin cancer. Illustration by Mekhi Baldwin

Skin cancer responds best to treatment when you catch it early. Melanoma, the third most common type of skin cancer, is the most dangerous type. It tends to spread to other body parts, including vital organs. When a melanoma spot reaches the size of a dime on your skin, it has a 50% chance of spreading.

Five telltale signs can help you recognize melanoma. You can use the ABCDE rule for skin cancer to help you remember them:

1. Asymmetry

With melanoma, one-half of the spot is not like the other half.

2. Border

A melanoma spot has an irregular or scalloped border. The border is not clearly defined.

3. Color

Melanoma varies in color from one area to the next. This includes shades and areas of:

  • tan
  • brown
  • black
  • white
  • blue
  • red

4. Diameter

Melanoma spots are typically larger than 6 millimeters. This is about the size of a pea or pencil eraser. However, melanomas may be smaller than this at the time of diagnosis.

5. Evolving

It is important to monitor the spot. It may evolve or change in size, shape, or color.

What are the signs and symptoms of skin cancer?

In addition to the ABCDEs of melanoma, the most common sign of skin cancer is a change in your skin. Not all cancers look the same, but signs to look for include:

  • new growth
  • change in a current growth or mole
  • sore that will not heal

How do you check your skin for skin cancer?

You can increase your chances of spotting skin cancer early by checking your skin regularly. Here are steps for checking your skin for skin cancer:

  1. Scan your body while standing in front of a long mirror: Examine your body front and back in a mirror. Raise each arm to look at your sides, right and left.
  2. Check your underarms, forearms, and palms: With your elbows bent, look carefully at your palms, forearms, and underarms.
  3. Check your legs, toes, and the soles of your feet: Look at your legs, front and back. Examine your feet and toes, including between your toes and the bottom of your feet.
  4. Check your neck and scalp: Use a hand mirror to look closely at your scalp and the back of your neck. Separate your hair for a closer look at your scalp.
  5. Check your back and buttocks: Finally, check your back and buttocks with a hand mirror.

What are the types of skin cancer?

There are three major types of skin cancers, which all begin in the epidermis (the outermost layer of skin):

Squamous cell carcinoma

Squamous cell carcinoma is a type of skin cancer that:

  • begins in the squamous cells, which make up the top layer of the epidermis
  • is most common in people with light skin but can also develop in those with dark skin
  • can be a scaly patch, red bump, or sore that does not heal 
  • can be a sore that heals and then reopens
  • tends to form on skin that gets frequent sun exposure

Basal cell carcinoma

Basal cell carcinoma is a type of skin cancer that:

  • starts in the basal cells, which are below the squamous cells
  • often develops in people with light skin but can also develop in people with dark skin
  • can appear as a round, pink or skin-colored growth, bump, or patch
  • often develops from frequent sun exposure or indoor tanning
  • often occurs on the head, neck, and arms but can form anywhere on the body


Melanoma is a type of skin cancer that:

  • begins in the melanocytes, the cells that make melanin, which gives skin its pigment or color
  • is often considered the most serious skin cancer because it tends to spread
  • can develop within a mole or as a dark spot that looks different from the rest of your skin

Other rare skin cancer types

Rarer types of skin cancer include:

  • Merkel cell carcinoma, a rare and aggressive cancer that occurs when Merkel cells grow out of control
  • cutaneous T cell lymphoma, a rare type of blood cancer that starts in white blood cells that can then affect the skin
  • Kaposi’s sarcoma, which develops from cells that line lymph or blood vessels
  • dermatofibrosarcoma protuberans, which begin in connective tissue cells in the middle layer of skin and tend to grow slowly
  • sebaceous carcinoma, an aggressive skin cancer that usually begins in a sebaceous gland on an eyelid

When should you contact a doctor?

Doctor checking a person's skin and taking a picture of a spot
Irina Efremova/Stocksy United

In addition to self-exams for skin cancer, it is important to get annual checkups from a board-certified dermatologist. They can examine your skin for any changes, such as a new growth or spot.

Contact your dermatologist if you notice:

  • a change in an old growth or spot
  • spots that are different from others
  • spots that are itching or bleeding
  • a sore that will not heal
  • one or more ABCDEs of melanoma


The ABCDEs of melanoma are five visible skin features that are characteristic of early melanoma, one of the most common types of skin cancer.

Other common types of skin cancer include squamous cell and basal cell carcinomas. Melanoma is the most dangerous type because it spreads to other body parts, including vital organs. As such, it is important to catch it early.

You can increase your chances of early detection with self-exams and annual checks from a board-certified dermatologist. Contact your dermatologist if you notice skin changes, such as a new spot, a sore that will not heal, or any of the ABCDEs of melanoma.

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Medical Reviewer: Raechele Cochran Gathers, MD
Last Review Date: 2022 Sep 16
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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  4. Kaposi sarcoma. (n.d.).
  5. Skin cancer types: Dermatofibrosarcoma protuberans overview. (n.d.).
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  7. Varghese, T., et al. (2021). T-cell lymphoma.
  8. What are the symptoms? (2022).
  9. What is skin cancer? (2022).
  10. What to look for: ABCDEs of melanoma. (n.d.).