These 5 “Dark Spots” on Your Body May Be Warning Signs of Cancer

Dark spots on the skin or elsewhere on the body can have many causes — from harmless age spots to potentially serious signs of cancer. While most dark patches are benign, certain kinds of changes should prompt further evaluation by a healthcare provider, especially a dermatologist. Early detection of cancer greatly improves treatment outcomes.

🔎 1. New or Changing Dark Mole (Melanoma Warning)

A new dark spot, or a mole that is changing in size, shape, or color, may be a warning sign of melanoma — the deadliest form of skin cancer. Melanoma often appears as an irregular patch with uneven color or an unusual shape.

Dermatologists use the ABCDE rule to help identify melanoma:

• A – Asymmetry: one half of the mole doesn’t match the other

• B – Border: edges are irregular or blurred

• C – Color: multiple colors or uneven shading

• D – Diameter: larger than 6 mm (about the size of a pencil eraser)

• E – Evolving: changes over time in size, color, or shape

If you notice any mole that fits these criteria, see a doctor promptly.

📍 2. Dark Streaks Under Nails (Subungual Melanoma)

A dark line or streak under a fingernail or toenail can sometimes signify subungual melanoma, a rare but serious type of skin cancer. This spot may be confused with a bruise, but unlike typical injuries, it doesn’t heal over time.

Such streaks can also appear around the nail and may widen or deepen.

🟤 3. Dark, Irregular Patches in Non-Sun-exposed Areas

In people with darker skin tones, melanomas may appear on areas not typically exposed to the sun — such as the palms, soles, nail beds, inside the mouth, or genital areas. These spots might look like irregular dark patches rather than classic sun-induced moles.

Any dark area that seems unusual or is changing deserves evaluation.

📈 4. New or Changing Spots That Don’t Heal

Spot types like:

• A bump or mole that bleeds or itches

• A sore that doesn’t heal

• A patch that crusts over repeatedly

may indicate basal cell carcinoma or squamous cell carcinoma — other common skin cancers. These often begin as new growths that don’t go away with typical care.

Basal and squamous cell cancers are usually highly treatable if caught early, but letting them go longer increases health risks.

🩹 5. Dark Spots That Look Different from Others (“Ugly Duckling Sign”)

Even a spot that doesn’t clearly fit the ABCDE criteria may still be suspicious if it looks significantly different from other spots on your skin. This “ugly duckling” pattern — where one mole clearly stands out — can be an early warning sign of melanoma.

Dermatologists encourage regular self-exams, looking for any spot that seems out of place.

🧠 When to See a Doctor

You should consult a healthcare professional if you notice:

• A new spot that wasn’t there before

• A spot that changes over weeks or months

• A patch that bleeds, itches, or won’t heal

• A discoloration under a nail

• A dark area that stands out from other spots

Even if a spot turns out to be harmless, a doctor can reassure you and help monitor any changes over time.

🩺 How These Signs Relate to Cancer

Not all dark spots are cancerous — examples like “cherry angiomas” or common lentigines are benign. But persistent, changing, or unusual dark spots can indicate early skin cancer.

Regular skin checks and sun protection (broad-spectrum sunscreen, protective clothing) are key to prevention and early detection.

🧩 Summary — 5 Dark Spots to Watch For

1. New or evolving mole with asymmetry or multiple colors — possible melanoma

2. Dark streaks under nails — possible subungual melanoma

3. Dark patches in non-sun-exposed areas — melanoma in unexpected sites

4. Persistent sores or irregular growths — basal/squamous cell carcinoma

5. Spot that looks different from the rest — “ugly duckling” warning