Skip to content Certain cancers, particularly cancers affecting the blood and bone marrow, can interfere with normal blood-cell production.
Platelets are especially important because they help blood clot.
When platelet levels become too low, a person may bruise or bleed more easily.
The National Cancer Institute notes that low platelet counts can cause increased bruising or bleeding and tiny red or purple spots on the skin called petechiae.
Some forms of leukemia can also produce easy bruising or bleeding.
For example, the National Cancer Institute lists easy bruising or bleeding among possible symptoms of acute lymphoblastic leukemia and acute myeloid leukemia.
But there is a crucial distinction:
**A person with unexplained bruising does not necessarily have leukemia or another cancer.**
The same symptoms can occur with many noncancerous conditions.
That’s why doctors don’t diagnose cancer simply by looking at a bruise.
## The Pattern Matters
One isolated bruise after an unexplained bump is usually very different from a pattern of increasingly frequent, unexplained bruises.
Pay attention if bruises:
* Appear frequently without obvious injuries
* Become unusually large
* Appear suddenly when this isn’t normal for you
* Keep appearing in different areas
* Occur alongside unusual bleeding
* Take unusually long to disappear
* Are accompanied by other unexplained symptoms
These circumstances don’t prove that something serious is happening.