Rarely, cancers in the nose can result in nosebleeds, explains WebMD. Patients with acute promyelocytic leukemia, a form of acute myeloid leukemia, may also develop nosebleeds due to a decrease in the body's blood-clotting abilities, notes the American Cancer Society.
Although breast cancer itself does not cause nosebleeds, breast cancer patients often experience nosebleeds as a side effect of their treatments that reduce their platelet counts, states BreastCancer.org.
Avastin is one example of a targeted breast cancer therapy that lowers platelet levels. Platelets are blood cells that gather near injuries and cuts to form blood clots in healthy individuals. Small amounts of force, such as from blowing one's nose or lightly bumping into something, can cause a nosebleed when there is an insufficient amount of platelets in the bloodstream. Diminished platelet levels are also the reason for an increased incidence of nosebleeds in acute promyelocytic leukemia patients, explains the American Cancer Society.
There are numerous other causes of nosebleeds outside of cancer, notes WebMD. The most common cause is trauma to the nose. This trauma can occur on the outside of the nose, such as when a ball hits a person in the face, or on the inside of the nose, such as from irritation due to a cold. Medications that thin the blood, such as aspirin, and liver disease are other potential causes of nosebleeds.