The ABCDE rule is a dermatologist-developed mnemonic for identifying moles that warrant professional evaluation. It stands for Asymmetry, Border, Color, Diameter, and Evolution. Use this interactive guide to understand each criterion, apply it to your own moles, and determine if a dermatologist visit is warranted.
Asymmetry
Draw an imaginary line through the center of the mole. In a benign (normal) mole, both halves match. In a potentially concerning mole, the two halves look different.
Border
Benign moles have smooth, well-defined borders. Concerning moles may have ragged, notched, blurred, or irregular edges that fade into surrounding skin.
Color
Benign moles are typically a single shade of tan or brown. Concerning moles may show multiple shades of brown, black, red, white, or blue within the same lesion.
Diameter
Most melanomas are larger than 6mm (about the size of a pencil eraser) when diagnosed. However, melanomas can be smaller when caught early — size alone is not definitive.
Evolution
Evolution is often considered the most critical criterion. Any mole that changes over weeks to months — in size, shape, color, or texture — deserves prompt professional evaluation.
Signs of concerning evolution:
- Increasing in size over weeks or months
- Changing color or developing new shades
- Changing shape or developing irregular edges
- Bleeding without injury
- Itching, crusting, or becoming painful
- New mole appearing in adulthood (especially after 50)
ABCDE Assessment Result
Additional Risk Factors to Discuss With Your Dermatologist
How to Perform a ABCDE Mole Self-Assessment
The ABCDE self-examination is a systematic method for evaluating moles that can help you identify changes that warrant professional attention. It takes only a few minutes and is recommended monthly.
Preparation
You will need: a full-length mirror, a hand mirror for hard-to-see areas, and good lighting. Optionally, photograph concerning moles with your phone for comparison at future checks. Perform your self-exam after a shower in a well-lit room.
Systematic Body Check
Check your entire skin surface systematically: face, scalp (use a comb to part hair), neck, chest, abdomen, arms and hands (including between fingers and under nails), back (use the hand mirror), buttocks and genitals, legs and feet (including between toes and sole). Do not skip areas just because they are rarely sun-exposed — melanoma can develop anywhere.
Applying ABCDE to Each Mole
For each mole you are evaluating: check symmetry by imagining a line through the center; examine the borders with good lighting; note all colors present; estimate the diameter compared to a pencil eraser (6mm); and compare to photos from previous months if available. A mole that meets two or more criteria deserves dermatologist evaluation.
When to Act Immediately
See a dermatologist urgently (within days) if a mole bleeds without injury, grows rapidly over weeks, or causes persistent pain or itching. For other concerning ABCDE findings without emergency symptoms, aim to schedule an appointment within 2-4 weeks. Early-stage melanoma has a 5-year survival rate over 99% — early detection is critical.
FAQ
Is this skin cancer guide free?
Yes, completely free with no signup required. All information runs locally in your browser.
Can this diagnose skin cancer?
No. This is an educational guide only. It cannot diagnose skin cancer or melanoma. Only a licensed dermatologist using clinical examination and possibly dermoscopy or biopsy can diagnose skin cancer. See a dermatologist for any mole that concerns you.
What does ABCDE stand for in skin cancer detection?
ABCDE stands for: A = Asymmetry (one half doesn't match the other), B = Border (irregular, ragged, or blurred edges), C = Color (variation in shades of brown, black, red, white, or blue), D = Diameter (larger than 6mm, about the size of a pencil eraser), E = Evolution (any change in size, shape, color, or new symptoms like bleeding or itching).
What is the most important letter in ABCDE?
Evolution (E) is considered by many dermatologists to be the most important criterion. Any changing mole deserves prompt evaluation regardless of the other ABCDE factors. A melanoma that is caught early because it was changing is more treatable than one noticed only when it is large.
All my moles are large — is that concerning?
Diameter alone (D criterion) is the least specific ABCDE factor. Some benign moles are larger than 6mm, while some melanomas start smaller. Diameter is most concerning in combination with other criteria (asymmetry, irregular borders, color variation). If you have many large moles, a dermatologist can evaluate them and establish a baseline for monitoring.
How often should I check my skin?
Monthly self-examinations are recommended. Use a full-length mirror and a hand mirror to check all areas including the scalp, between fingers and toes, and the soles of the feet. Take photos of moles to compare over time. Annual professional skin exams are recommended for adults, and more frequently for those with risk factors.
What are risk factors for melanoma beyond ABCDE?
Major risk factors include: fair skin, light hair, light eyes; a history of sunburns (especially blistering burns in childhood); more than 50 moles; family history of melanoma; personal history of skin cancer; immunosuppression; and extensive lifetime UV exposure or use of tanning beds.
When should I see a dermatologist urgently?
See a dermatologist urgently (within days) if a mole: bleeds without injury, is rapidly growing, itches persistently, changes color or shape quickly, or if you have a sore that does not heal within a few weeks. For non-urgent but concerning changes, aim for an appointment within 2-4 weeks.