Is Unexplained Bruising a Sign of Cancer?

This page is for people who have bruises they cannot explain and wonder if it could be cancer. It covers a simple check you can do, the common causes, and when to call your care team.

A bruise is itself bleeding into the skin. Blood leaks out of small vessels and collects under the surface. That is why a simple press can tell a bruise or other bleeding apart from ordinary redness.

MedlinePlus explains it: areas of bleeding into the skin do not become paler when you press on them, the way redness does.

Press a fingertip on the mark, hold for a second, and lift. If the color fades and then floods back, that is redness. If the color stays as it was, blood has leaked into the skin. That is true of an ordinary bruise too.

So pressing tells you whether a mark is bleeding into the skin. It does not tell you whether a bruise is harmless. For that, what matters is the cause, whether it goes away, and what else is happening, which the sections below cover.

MedlinePlus separates bleeding into the skin by scale.

Tiny red dots from broken blood vessels are called petechiae. Larger flat areas where blood has collected under the tissue are purpura. A very large bruised area is an ecchymosis.

Then comes the sentence that sets the priority. Aside from the common bruise, MedlinePlus says bleeding into the skin or mucous membranes is a very significant sign and should always be checked out by a health care provider.

Mucous membranes means the lining of the mouth and the gums, so bleeding there counts too.

The causes MedlinePlus lists run from ordinary to serious, and most are ordinary.

• Injury or trauma.
• Aging skin, which bruises from knocks you do not remember.
• Blood thinners such as warfarin or heparin, plus aspirin and steroids.
• Antiplatelet medicines such as clopidogrel.
• Viral infections that affect clotting.
• Allergic reactions.
• Autoimmune disorders, where the immune system attacks the body.
• Low platelet count. Platelets are blood cells that help blood clot.
• Chemotherapy and radiation.
• Leukemia.
• Blood poisoning.

Skin on the forearms and backs of the hands thins with age and sun exposure, and the bruises that follow can look alarming while meaning very little.

MedlinePlus gives two triggers for contacting your provider: sudden bleeding into the skin for no apparent reason, and unexplained bruising that does not go away. Its page on low platelets adds a third, unexplained bleeding or bruising of any kind.

None of those are described as emergencies. They are reasons to pick up the phone rather than wait another month. MedlinePlus's page on bruises adds one that is more urgent: contact your provider right away if you feel extreme pressure in a bruised area, especially if it is large or very painful.

What does need the emergency room is heavy bleeding. MedlinePlus says to call 911 or go to the nearest emergency room if you vomit blood or material that looks like coffee grounds, have black tarry stools or a lot of blood in your stool, feel lightheaded or dizzy from bleeding, have chest pain or trouble breathing, or have severe abdominal pain with the bleeding. Do not drive yourself.

Easy bruising is on the leukemia symptom list, but it does not travel alone.

NCI says the signs of acute myeloid leukemia include fever, feeling tired, and easy bruising or bleeding. Its full list adds weakness, infection, paleness or loss of normal skin color, and bleeding. It notes that early symptoms may resemble flu or other common illnesses.

That combination is the thing to weigh. A single bruise on a shin, in someone who plays sports and takes aspirin, is a different picture from weeks of bruising plus fever plus exhaustion plus bleeding gums.

A complete blood count (CBC) can answer much of this.

It measures platelets, red cells and white cells at once, which covers low platelets, anemia (low red blood cells) and abnormal white cell numbers together. Blood clotting tests and liver tests may be added.

Before that appointment, photograph the marks with a ruler beside them, and list every medicine and supplement, including aspirin, fish oil and herbal remedies. Note whether bleeding happens elsewhere: gums when brushing, nosebleeds, heavier periods. How Cancer Is Diagnosed explains what blood tests can and cannot show.

• MedlinePlus — Bleeding into the skin
• MedlinePlus — Bruise
• MedlinePlus — Thrombocytopenia
• MedlinePlus — Gastrointestinal bleeding
• National Cancer Institute — Adult Acute Myeloid Leukemia Treatment (PDQ)