Platelets are tiny, colorless cell fragments that stop bleeding by forming clots. Normal platelet counts range from 150,000 to 450,000/microliter. While “platelet cancer” isn’t a medical diagnosis, changes in platelet counts or function can link to various cancers. This article explains medical conditions where cancer affects platelet levels or function.
The Connection Between Platelets and Cancer
Platelets are involved with cancer in two ways: through high counts (thrombocytosis) or low counts (thrombocytopenia). Both can indicate malignancy or be a direct consequence of cancer or its treatment.
High platelet counts (thrombocytosis) can occur with cancer. Myeloproliferative Neoplasms (MPNs) are conditions where the bone marrow produces too many blood cells, including platelets. Essential Thrombocythemia (ET) is an MPN marked by platelet overproduction and is a chronic blood cancer. Polycythemia Vera (PV), another MPN, mainly involves excess red blood cells but can also raise platelet counts. These conditions often result from genetic mutations (e.g., JAK2, CALR, MPL).
High platelet counts can also be a reactive response to cancer (secondary or reactive thrombocytosis). The cancer or associated inflammation triggers increased platelet production. Tumors release inflammatory cytokines, like interleukin-6 (IL-6), which stimulate thrombopoietin production, promoting platelet formation. Reactive thrombocytosis is more common than primary thrombocytosis and often occurs with solid tumors such as lung, colon, ovarian, and stomach cancers.
Low platelet counts (thrombocytopenia) can link to cancer. Cancers like leukemias and lymphomas directly affect the bone marrow, reducing platelet formation. Cancer treatments, especially chemotherapy and radiation, commonly cause thrombocytopenia. Chemotherapy drugs damage rapidly dividing bone marrow cells, including megakaryocytes, which produce platelets. This bone marrow suppression temporarily lowers platelet counts, often peaking at their lowest 10-14 days after chemotherapy.
Recognizing Signs and Symptoms
Abnormal platelet counts, high or low, can cause various signs and symptoms warranting medical attention, especially with other general cancer indicators. Recognizing these can prompt early evaluation.
With high platelet counts (thrombocytosis), symptoms often relate to blood clots, though some individuals have no symptoms. Signs of blood clots include headaches, dizziness, vision changes, or weakness. Pain, redness, swelling, or warmth in the legs or arms can also indicate deep vein thrombosis. Paradoxically, very high platelet levels can impair platelet function, leading to unusual bleeding like nosebleeds, easy bruising, or bleeding from the mouth or gums.
Conversely, low platelet counts (thrombocytopenia) increase bleeding tendency. This can appear as easy bruising, small red or purple pinpoint spots (petechiae), or prolonged bleeding from minor cuts. Other bleeding signs include frequent nosebleeds, bleeding gums, blood in urine or stool, or unusually heavy menstrual bleeding.
Severe headaches, worsening weakness, or blurred vision can also occur. These platelet-related symptoms may appear alongside general cancer signs, such as unexplained weight loss, persistent fatigue, fever, or night sweats. Any new or unexplained symptoms should be discussed with a healthcare provider.
Diagnosis and Treatment Approaches
Diagnosing conditions involving platelets and cancer begins with routine blood tests, progressing to specific investigations to identify the underlying cause. Treatment strategies depend on whether platelet counts are high or low and the nature of the associated cancer.
Diagnosis begins with a complete blood count (CBC), measuring platelets, red blood cells, and white blood cells. A platelet count outside the normal range (150,000-450,000/microliter) prompts further evaluation. If abnormal counts are detected, additional blood tests may check for inflammation markers or specific genetic mutations. For high platelet counts, especially when an MPN is suspected, genetic testing for mutations like JAK2, CALR, or MPL is common, as these are frequently found in Essential Thrombocythemia and Polycythemia Vera.
A bone marrow biopsy may be recommended to examine platelet-producing cells and confirm an MPN or other bone marrow disorders. This involves taking a small sample of bone marrow fluid and tissue, typically from the hip bone, for microscopic analysis and genetic testing. Imaging scans may also identify solid tumors causing reactive thrombocytosis or assess for cancer spread causing thrombocytopenia.
Treatment for high platelet counts with MPNs often involves medications to reduce bone marrow platelet production. Hydroxyurea is a common medication that suppresses blood cell production and lowers platelet levels. Anagrelide interferes with platelet maturation. Low-dose aspirin is frequently prescribed to reduce blood clot risk, a common complication. For advanced MPNs, targeted therapies or allogeneic hematopoietic stem cell transplantation may be considered, with the latter being the only potentially curative option.
Managing low platelet counts in cancer patients focuses on addressing the cause and preventing bleeding. If thrombocytopenia is a chemotherapy side effect, doctors may adjust doses, delay treatments, or administer platelet transfusions for acute bleeding or very low counts (e.g., below 20,000 per microliter). Thrombopoietin receptor agonists (TPO-RAs), like romiplostim or eltrombopag, can stimulate bone marrow to produce more platelets, though their use for chemotherapy-induced thrombocytopenia is still being studied. Prognosis for individuals with platelet abnormalities linked to cancer varies widely, depending on cancer type, stage, overall health, and treatment response.