Neoplasm literally means "new growth." Myeloproliferative neoplasms (MPNs) are clonal diseases in which the bone marrow makes too many red blood cells, platelets, or certain white blood cells. MPNs usually get worse over time as the number of extra cells build up in the blood and/or bone marrow. This may cause bleeding problems, anemia, infection, fatigue, or other signs and symptoms. The myeloproliferative neoplastic conditions are more commonly diagnosed in older adults between 50 and 70 years of age and are rare in children. The MPNs have been known to progress into acute leukemias. Consequently, they are referred to as premalignant conditions.
MPNs are classified according to the cell line that is predominantly affected, taking into account the clinical aspects, laboratory test results, and genetic findings. The older French-American-British (FAB) classification system and the more recent World Health Organization (WHO) classification system both provide guidelines to assist with classifying and diagnosing MPNs. This course will refer to the criteria established by WHO, which are more commonly used.
The image shown depicts the clonal proliferation of abnormal cells due to disease-initiating mutations. As these cells grow in number, patient symptoms and disease severity increases.
Myeloproliferative Neoplasm Development. Image adapted from Washington University School of Medicine in St. Louis, Divisions of Hematology and Oncology. http://hematology.im.wustl.edu/people/faculty/Oh/Oh_Res.html