Dermatology
What Are the Warning Signs of Skin Cancer?
Last reviewed: May 2026 · Haute MD Editorial Team
The most important warning signs of skin cancer are captured in the ABCDE rule for melanoma: Asymmetry (one half does not match the other), Border irregularity (ragged, notched, or blurred edges), Color variation (multiple shades of brown, black, red, white, or blue), Diameter larger than 6mm (size of a pencil eraser), and Evolution (any mole or lesion that changes in size, shape, or color). Any mole or skin lesion that changes should be evaluated by a dermatologist promptly.
Warning signs of basal cell carcinoma
A pearly or translucent bump, a flat scar-like lesion that is flesh-colored or slightly pink, a pink growth with raised edges, a sore that bleeds, heals, and returns, or a sore that does not heal after several weeks.
Warning signs of squamous cell carcinoma
A firm, red nodule, a flat lesion with a scaly, crusted surface, a new sore or raised area on a scar, a rough, scaly patch on the lip, a red sore or rough patch inside the mouth, a wart-like growth, or a new sore that does not heal.
Warning signs of melanoma
In addition to the ABCDE criteria, watch for any mole that looks different from all other moles (the "ugly duckling" sign), a lesion with an unusual color, a lesion that itches, bleeds, or oozes without trauma, or a dark streak under a nail.
Frequently Asked Questions
What does a cancerous mole look like?
A cancerous mole may be asymmetrical, have irregular borders, show multiple colors, be larger than 6mm, or be changing. However, not all melanomas follow these criteria — any changing skin lesion should be evaluated.
Can skin cancer itch?
Yes. Itching, bleeding, or crusting of a mole or skin lesion can be a warning sign of skin cancer, though these features can also occur with benign lesions.
How quickly does skin cancer spread?
Basal cell carcinoma grows slowly and rarely spreads. Squamous cell carcinoma can spread to lymph nodes if untreated. Melanoma can spread rapidly and requires prompt treatment.
What should I do if I find a suspicious spot?
Schedule an appointment with a board-certified dermatologist promptly. Do not wait for a regular annual visit if you notice a new, changing, or suspicious lesion.
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