Lifestyle

5 Signs of Skin Cancer Most People Dismiss as Harmless

By Erica Coleman · June 29, 2026

Skin cancer is the most common cancer in the United States. Approximately 100,000 Americans will be diagnosed with invasive melanoma this year alone. The survival rate when caught early is 99%. When it spreads to distant organs, that number drops to 35%. The gap between those two numbers is what you see — and what you dismiss.

1. A mole that looks different from every other mole on your body

Dermatologists call this the “ugly duckling” sign — a mole that doesn’t match the rest. Most of your moles should look similar to each other in color, size, and shape. If one stands out — darker, larger, different texture, irregular border — that difference is the signal. It doesn’t mean it’s cancer. It means it needs to be evaluated by a dermatologist.

2. A spot that follows the ABCDEs

The ABCDE rule is the screening tool dermatologists developed to help people identify potential melanomas. Asymmetry — one half doesn’t match the other. Border — edges are uneven, ragged, or blurred. Color — multiple colors or shades within the same spot. Diameter — larger than a pencil eraser (about 6mm). Evolving — any change in size, shape, color, or height. Any single one of these features in a mole or skin spot warrants a professional look. Two or more together warrants an urgent appointment.

3. A sore that doesn’t heal within three weeks

A non-healing sore — one that bleeds, crusts over, appears to heal, then opens again — is one of the most common presentations of basal cell carcinoma, the most frequently diagnosed skin cancer. People dismiss these as cuts that keep getting irritated or dry patches that won’t go away. If a sore anywhere on your body has not healed within three weeks, show it to a doctor.

4. A dark streak under a fingernail or toenail

Melanoma can develop under nails — a subtype called acral melanoma that is more common in people with darker skin tones and is frequently diagnosed later because it’s not on sun-exposed skin. A dark brown or black vertical line running from the cuticle to the tip of a nail — especially on a single finger or toe — should be evaluated. Most nail streaks are harmless melanin deposits, but the ones that aren’t are aggressive.

5. A new spot that appeared after age 50

New moles can appear at any age, but the development of a genuinely new mole after age 50 is less common and more clinically significant than a new mole at 25. Any new pigmented spot that appears after 50 should be evaluated by a dermatologist, particularly if it is growing, changing color, or exhibits any of the ABCDE features.

The screening is simple: a full-body skin exam by a dermatologist takes 10 to 15 minutes. The American Academy of Dermatology recommends at least one professional skin exam per year — more frequently if you have a personal or family history of skin cancer, a history of severe sunburns, or light skin with many moles. Between appointments, a monthly self-check at home — head to toe, including your back, scalp, between your toes, and under your nails — is the habit that catches the things that change between visits.