Bruising (ecchymosis) occurs when small blood vessel leak blood into surrounding tissues. Platelets and clotting proteins normally limit this bleeding. In some cancers, whose protective mechanisms are weekended.

1. Low platelet counts (Thrombocytopenia)

Many cancers and some cancer treatments reduce platelet counts. When platelets are low, bruises may occur after minor bumps, and sometimes bruising appears without remembered injury. [1][2][3][4]

2. Treatment- and medication-related bleeding tendency

Rather than attributing bruising to “weakened vessel walls,” it is more accurate to note that some treatments and supportive medications used in cancer care can increase bruising risk—often by affecting platelet number/function or overall hemostasis. [1][3]

3. Coagulation (clotting) abnormalities

Some malignancies can disrupt the balance between clot formation and clot breakdown. In severe cases, disseminated intravascular coagulation (DIC) can occur and may present with both clotting complications and bleeding/bruising due to consumption of platelets and coagulation factors. [1][10]

4. Bone marrow suppression

The bone marrow is where platelets, red cells, and white cells are made. When marrow function is impaired by disease or treatment, platelet production can fall, increasing bruising and bleeding risk. [2][4][6]

In blood and bone marrow cancers, bruising most often reflects disruption of normal hemostasis—the body’s ability to stop small vessel bleeding. There are three common, overlapping pathways:

1. Reduced platelet production (thrombocytopenia)

Many hematologic malignancies affect the bone marrow environment. When healthy marrow is replaced or suppressed, platelet counts can fall, so bruises may appear after minimal trauma, and petechiae (tiny red-purple spots) may occur on the skin or mucosal surfaces. [6]

2. Platelet or clotting dysfunction (even when counts are not low)

Bruising can also occur when platelets are present but do not function normally, or when the coagulation system is imbalanced. In myeloproliferative neoplasms (including PV), bleeding/bruising may be linked to platelet dysfunction and, in some cases, acquired von Willebrand factor abnormalities, which impair early clot formation. [7][8][9]

3. Treatment- and medication-related effects

Cancer therapies and supportive medications may further increase bruising risk by lowering platelets, altering platelet function, or affecting coagulation balance. This is why new or worsening bruising during treatment should be assessed in clinical context, particularly if accompanied by other bleeding symptoms. [1]

Polycythemia vera is a chronic myeloproliferative neoplasm characterized by increased red blood cell production and, in many patients, increased platelets and/or white cells. [7][8] Although PV is often associated with thrombotic risk, bruising and mucosal bleeding can also occur. Contributing factors may include:

1. Platelet/von Willebrand factor abnormalities

Platelet count alone does not guarantee normal clot formation. In PV (and other MPNs), bleeding can be linked to platelet dysfunction and—particularly when platelet counts are extremely high—acquired von Willebrand factor abnormalities that impair primary hemostasis. [7][8][9]

2. Increased hematocrit and vascular complications

PV can increase blood viscosity and contribute to vascular complications. For bruising/bleeding risk, the more consistently supported drivers are platelet/von Willebrand factor abnormalities and the effect of antiplatelet therapy in susceptible patients, rather than assuming viscosity directly “ruptures” capillaries. [7][8][9]

3. Treatment-related bruising

Low-dose aspirin is commonly used in PV to reduce clot risk, but any antiplatelet therapy can increase bruising or bleeding tendency in some patients—especially when baseline hemostasis is impaired. [7][8]

While occasional bruises are normal, patients should talk to a clinician if they notice:

• Frequent or unexplained bruises
• Large or painful bruises
• Bleeding gums or recurrent nosebleeds
• Tiny red dots (petechiae) on the skin
• Prolonged bleeding from cuts or injections

These findings can indicate thrombocytopenia or coagulation dysfunction that warrants evaluation. [2][3][4]

Management depends on the cause and overall clinical context.

• Assessment commonly includes medication review and blood testing (e.g., CBC with platelet count; coagulation testing when indicated). [1][2]
• If platelets are low, clinicians address the underlying cause and use supportive care when appropriate. [1][2][3][4]
• For polycythemia vera, treatment is individualized but commonly includes hematocrit control (e.g., phlebotomy), low-dose aspirin when appropriate, and cytoreductive therapy in selected patients (including interferon-based options). [7][8]

Patients should minimize avoidable trauma, use gentle oral care, avoid non-prescribed antiplatelet/NSAID use, and report new bleeding or bruising promptly. [2][3][4]

PV — Polycythemia vera

MPN — Myeloproliferative neoplasm

MPNs — Myeloproliferative neoplasms

DIC — Disseminated intravascular coagulation

CBC — Complete blood count

NSAID — Nonsteroidal anti-inflammatory drug

1. Johnstone C, Rich SE. Bleeding in cancer patients and its treatment: a review. Annals of Palliative Medicine 2018;7(2):265–73.
2. NCBI Bookshelf. Excessive Bleeding and Bruising (clinical evaluation/approach). Available on https://www.ncbi.nlm.nih.gov/books/NBK253/pdf/Bookshelf_NBK253.pdf Accessed in Jan 2026.
3. National Cancer Institute. Bleeding and Bruising (and Cancer Treatment). Available on https://www.cancer.gov/about-cancer/treatment/side-effects/bleeding-bruising Accessed in Jan 2026.
4. American Cancer Society. Low platelet count (thrombocytopenia) and bleeding/bruising. Available on https://www.cancer.org/cancer/managing-cancer/side-effects/low-blood-counts/bleeding.html Accessed in Jan 2026.
5. Mayo Clinic. Leukemia—Symptoms and causes. Available on https://www.mayoclinic.org/diseases-conditions/leukemia/symptoms-causes/syc-20374373 Accessed in Jan 2026.
6. Cancer Research UK. Blood, bone marrow and cancer drug side effects (low platelets and bruising). Available on https://www.cancerresearchuk.org/about-cancer/treatment/cancer-drugs/side-effects/your-blood-and-bone-marrow Accessed in Jan 2026.
7. Tremblay D, et al. Diagnosis and Treatment of Polycythemia Vera: A Review. JAMA. 2025;333(2):153-60. https://pubmed.ncbi.nlm.nih.gov/39556352/
8. Lu, X., & Chang, R. Polycythemia vera. In StatPearls [Internet]. StatPearls Publishing. (Updated April 24, 2023). Available on https://www.ncbi.nlm.nih.gov/books/NBK557660/. Accessed in Jan 2026.
9. Nicol C, et al. Hemorrhages in Polycythemia Vera and Essential Thrombocythemia… Thrombosis and Haemostasis. Thrombosis and Haemostasis 2022;122(10):1712–22.
10. Levi M. Disseminated Intravascular Coagulation in Cancer: An Update. Seminars in Thrombosis and Hemostasis. Seminars in Thrombosis and Hemostasis 2019;45(04):342–7.