These conditions are relatively uncommon.Conditions where the secondary polycythemia is not caused by physiologic adaptation, and occurs irrespective of body needs include:
Neoplasms – Renal cell carcinoma  or liver tumors, von Hippel-Lindau disease, and endocrine abnormalities including pheochromocytoma and adrenal adenoma with Cushings syndrome. People whose testosterone levels are high because of the use of anabolic steroids, including athletes who abuse steroids, or people on testosterone replacement for hypogonadism or transgender hormone replacement therapy, may develop secondary polycythemia. Blood doping - Secondary polycythemia can be induced by endurance athletes that take erythropoietin-stimulating agents, receive blood transfusions, and take other measures to increase their red blood cell mass in an effort to increase oxygen transport capacity. Altered oxygen sensing
Inherited mutations in three genes which all result in increased stability of hypoxia-inducible factors, leading to increased erythropoietin production, have been shown to cause erythrocytosis:
Chuvash erythrocytosis is an autosomal recessive form of erythrocytosis which is endemic in  patients from the Chuvash Republic in Russia. Chuvash erythrocytosis is associated with homozygosity for a C598T mutation in the von Hippel-Lindau gene (VHL), which is needed for the destruction of hypoxia-inducible factors in the presence of oxygen. Clusters of patients with Chuvash erythrocytosis have been found in other populations, such as on the Italian island of Ischia, located in the Bay of Naples. PHD2 erythrocytosis: Heterozygosity for loss-of-function mutations of the PHD2 gene are associated with autosomal dominant  erythrocytosis and increased hypoxia-inducible factors activity. HIF2α erythrocytosis: Gain-of-function mutations in HIF2α are associated with autosomal dominant erythrocytosis and pulmonary hypertension.
In 2012, it represented 8.5% of cancer cases in men, making it the fourth-most common cancer in men. Also in 2012, the number of deaths was 700,000, having decreased slightly from 774,000 in 1990, making it the third-leading cause of cancer-related death (after lung cancer and liver cancer).Less than 5% of stomach cancers occur in people under 40 years of age, with 81.1% of that 5% in the age-group of 30 to 39 and 18.9% in the age-group of 20 to 29.In 2014, stomach cancer resulted in 0.61% of deaths (13,303 cases) in the U.S. In China, stomach cancer accounted for 3.56% of all deaths (324,439 cases). The highest rate of stomach cancer was in Mongolia, at 28 cases per 100,000 people.In the United Kingdom, stomach cancer is the 15th-most common cancer (around 7,100 people were diagnosed with stomach cancer in 2011), and it is the 10th-most common cause of cancer-related deaths (around 4,800 people died in 2012).Incidence and mortality rates of gastric cancer vary greatly in Africa. The GLOBOCAN system is currently the most widely used method to compare these rates between countries, but African incidence and mortality rates are seen to differ among countries, possibly due to the lack of universal access to a registry system for all countries. Variation as drastic as estimated rates from 0.3/100000 in Botswana to 20.3/100000 in Mali have been observed. In Uganda, the incidence of gastric cancer has increased from the 1960s measurement of 0.8/100000 to 5.6/100000.