According to a Dutch source juvenile pilocytic astrocytoma occurs at a rate of 2 in 100,000 people. Most affected are children ages 5–14 years. According to the National Cancer Institute more than 80% of astrocytomas located in the cerebellum are low grade (pilocytic grade I) and often cystic; most of the remainder are diffuse grade II astrocytomas.

Tumors of the optic pathway account for 3.6-6% of pediatric brain tumors, 60% of which are juvenile pilocytic astrocytomas. Astrocytomas account for 50% of pediatric primary central nervous system tumors. About 80-85% of cerebellar astrocytomas are juvenile pilocytic astrocytomas.

Recent genetic studies of pilocytic astrocytomas show that some sporadic cases have gain in chromosome 7q34 involving the BRAF locus.

A degenerative breakdown of collagen, elastin, and smooth muscle caused by aging contributes to weakening of the wall of the artery.

In the aorta, this can result in the formation of a fusiform aneurysm. There is also increased risk of aortic dissection.

Medulloepithelioma carries a dismal prognosis with a median survival of 5 months.

Familial thoracic aortic aneurysm is an autosomal dominant disorder of large arteries.

There is an association between familial thoracic aortic aneurysm, Marfan syndrome and massive baclofen overdose as well as other hereditary connective tissue disorders.

Hamartomas, while generally benign, can cause problems due to their location. For example, when located on the skin, especially on the face or neck, they can be very disfiguring. Cases have been reported of hamartomas the size of a small orange. They may obstruct practically any organ in the body, such as the colon, eye, etc. They are particularly likely to cause major health issues when located in the hypothalamus, kidneys, lips, or spleen. They can be removed surgically if necessary, and are not likely to recur. Prognosis will depend upon the location and size of the lesion, as well as the overall health of the patient.

Establishing the incidence of aortic dissection has been difficult because many cases are only diagnosed after death (which may have been attributed to another cause), and is often initially misdiagnosed. Aortic dissection affects an estimated 2.0–3.5 people per every 100,000 every year. Studies from Sweden suggest that the incidence of aortic dissection may be rising. Men are more commonly affected than women: 65% of all people with aortic dissection are male. The mean age at diagnosis is 63 years. In females before the age of 40, half of all aortic dissections occur during pregnancy (typically in the third trimester or early postpartum period).

Right-sided aortic arch is rare, with a prevalence among adults of about 0.01%.

Grade I pilocytic astrocytoma and cerebellar gliomas are not associated with recurrence after complete resection. Grade II astrocytomas and cerebellar gliomas are more likely to recur after surgical removal. Pilomyxoid astrocytomas may behave more aggressively than classic pilocytic astrocytoma.

After complete surgical removal, in cases of progressive/recurrent disease or when maximal surgical removal has been achieved, chemotherapy and/or radiation therapy will be considered by the medical team.

Although the exact cause is unknown, some risk factors associated with individuals with IAA are:

Tobacco Use: Cigarette smoking and other forms of tobacco use appear to increase your risk of aortic aneurysms. In addition to the damaging effects that smoking causes directly to the arteries, smoking contributes to the buildup of fatty plaques in your arteries (atherosclerosis) and high blood pressure. Smoking can also cause your aneurysm to grow faster by further damaging your aorta.

Hardening of the arteries (atherosclerosis). Atherosclerosis occurs when fat and other substances build up on the lining of a blood vessel, increasing your risk of an aneurysm.

Infection in the aorta (vasculitis). In rare cases, abdominal aortic aneurysm may be caused by an infection or inflammation that weakens a section of the aortic wall.

Each year in the United States, some 45,000 people die from diseases of the aorta and its branches. Acute aortic dissection, a life-threatening event due to a tear in the aortic wall, affects 5 to 10 patients per million population each year, most often men between the ages of 50 and 70; of those that occur in women younger than 40, nearly half arise during pregnancy. The majority of these deaths occur as a result of complications of thoracic aneurysmal disease.

Paragangliomas originate from paraganglia in chromaffin-negative glomus cells derived from the embryonic neural crest, functioning as part of the sympathetic nervous system (a branch of the autonomic nervous system). These cells normally act as special chemoreceptors located along blood vessels, particularly in the carotid bodies (at the bifurcation of the common carotid artery in the neck) and in aortic bodies (near the aortic arch).

Accordingly, paragangliomas are categorised as originating from a neural cell line in the World Health Organization classification of neuroendocrine tumors. In the categorization proposed by Wick, paragangliomas belong to group II. Given the fact that they originate from cells of the orthosympathetic system, paragangliomas are closely related to pheochromocytomas, which however are chromaffin-positive.

Hypertension and cigarette smoking are the most important risk factors, though the importance of genetic factors has been increasingly recognized. Approximately 10% of patients may have other family members who have aortic aneurysms. It is also important to note that individuals with a history of aneurysms in other parts of the body have a higher chance of developing a thoracic aortic aneurysm.

A paraganglioma is a rare neuroendocrine neoplasm that may develop at various body sites (including the head, neck, thorax and abdomen). Unlike other types of cancer, there is no test that determines benign from malignant tumors; long-term followup is therefore recommended for all individuals with paraganglioma. Approximately 50% of patients with recurrent disease experience distant metastasis. The five-year survival in the setting of metastatic disease is 40% to 45%.

Of all people with aortic dissection, 40% die immediately and do not reach a hospital in time. Of the remainder, 1% die every hour, making prompt diagnosis and treatment a priority. Even after diagnosis, 5–20% die during surgery or in the immediate postoperative period. In ascending aortic dissection, if surgery is decided to be not appropriate, 75% die within 2 weeks. With aggressive treatment, 30-day survival for thoracic dissections may be as high as 90%.

An aortic aneurysm can occur as a result of trauma, infection, or, most commonly, from an intrinsic abnormality in the elastin and collagen components of the aortic wall. While definite genetic abnormalities were identified in true genetic syndromes (Marfan, Elher-Danlos and others) associated with aortic aneurysms, both thoracic and abdominal aortic aneurysms demonstrate a strong genetic component in their aetiology.

The occurrence of AAA varies by ethnicity. In the United Kingdom the rate of AAA in Caucasian men older than 65 years is about 4.7%, while in Asian men it is 0.45%. It is also less common in individuals of African, and Hispanic heritage. They occur four times more often in men than women.

There are at least 13,000 deaths yearly in the U.S. secondary to AAA rupture. The peak number of new cases per year among males is around 70 years of age, the percentage of males affected over 60 years is 2–6%. The frequency is much higher in smokers than in non-smokers (8:1), and the risk decreases slowly after smoking cessation. In the U.S., the incidence of AAA is 2–4% in the adult population.

Rupture of the AAA occurs in 1–3% of men aged 65 or more, the mortality is 70–95%.

Mortality from aortic rupture is up to 90%. 65–75% of patients die before they arrive at hospital and up to 90% die before they reach the operating room.

Medulloepithelioma most commonly affect children between 6 months and 5 years; rarely, this tumour may occur congenitally or beyond this age range. Incidence is equal in males and females.

The risk of aneurysm enlargement may be diminished with attention to the patient's blood pressure, smoking and cholesterol levels. There have been proposals to introduce ultrasound scans as a screening tool for those most at risk: men over the age of 65. The tetracycline antibiotic doxycycline is currently being investigated for use as a potential drug in the prevention of aortic aneurysm due to its metalloproteinase inhibitor and collagen stabilizing properties. In contrast, fluoroquinolones antibiotics are being investigated as a potential contributor to aortic aneurysms, given their tendency to break down collagen fibrils.

Anacetrapib is a cholesteryl ester transfer protein inhibitor that raises high-density lipoprotein (HDL) cholesterol and reduces low-density lipoprotein (LDL) cholesterol.

Anacetrapib reduces progression of atherosclerosis, mainly by reducing non-HDL-cholesterol, improves lesion stability and adds to the beneficial effects of atorvastatin

Elevating the amount of HDL cholesterol in the abdominal area of the aortic artery in mice both reduced the size of aneurysms that had already grown and prevented abdominal aortic aneurysms from forming at all. In short, raising HDL cholesterol is beneficial because it induces programmed cell death. The walls of a failing aorta are replaced and strengthened. New lesions should not form at all when using this drug.

The exact causes of the degenerative process remain unclear. There are, however, some hypotheses and well-defined risk factors.

- Tobacco smoking: More than 90% of people who develop an AAA have smoked at some point in their lives.

- Alcohol and hypertension: The inflammation caused by prolonged use of alcohol and hypertensive effects from abdominal edema which leads to hemorrhoids, esophageal varices, and other conditions, is also considered a long-term cause of AAA.

- Genetic influences: The influence of genetic factors is high. AAA is four to six times more common in male siblings of known patients, with a risk of 20-30%. The high familial prevalence rate is most notable in male individuals. There are many hypotheses about the exact genetic disorder that could cause higher incidence of AAA among male members of the affected families. Some presumed that the influence of alpha 1-antitrypsin deficiency could be crucial, while other experimental works favored the hypothesis of X-linked mutation, which would explain the lower incidence in heterozygous females. Other hypotheses of genetic causes have also been formulated. Connective tissue disorders, such as Marfan syndrome and Ehlers-Danlos syndrome, have also been strongly associated with AAA. Both relapsing polychondritis and pseudoxanthoma elasticum may cause abdominal aortic aneurysm.

- Atherosclerosis: The AAA was long considered to be caused by atherosclerosis, because the walls of the AAA frequently carry an atherosclerotic burden. However, this hypothesis cannot be used to explain the initial defect and the development of occlusion, which is observed in the process.

- Other causes of the development of AAA include: infection, trauma, arteritis, and cystic medial necrosis.

Little is known regarding the exact causes of aortic arch anomalies. However, the association with chromosome 22q11 deletion (CATCH 22) implies that a genetic component is likely in certain cases. Esophageal atresia also occurs in some patients with double aortic arch.

Inheritance is thought to be rather complex. There is a good amount of evidence that shows the disease is autosomal dominant, with some penetrance. There is also the possibility of age related dependence. It is known that Marfan’s Syndrome and Ehler-Danlos Syndrome lead to an increased risk for development of FAD. Marfan’s Syndrome is not required to have an aortic dissection. One study suggests that the chromosomal locus for the gene is 5q13-14. The same study found that other genes may be linked, and include loci for Marfan and Ehler-Danlos Syndromes, genes for metalloproteinase 3 and 9, and tissue inhibitor of malloproteinase 2 as well as two loci on chromosomes 5q13-14 and lq23.2-24. Still other studies show that mutations in smooth muscle cell-specific isoforms of alpha actin and beta myosin heavy chain may cause FAD. Mutations in the genes TGFBR 1 and 2 are known to cause dissections in aortas with normal diameter size (>4.3 cm) and gene "FPN1" mutations typically affect aortas with larger diameters (<4.4 cm).

There are several hypotheses which attempt to explain how the dissection physically occurs. The first states that a tear develops in the intima layer of the aorta which allows blood to flow from the lumen of the aorta into the intima. This event creates a dissection and essentially two lumens. The second hypothesis suggests that the vasa vasorum ruptures and causes a hemorrhage in the wall of the aorta. The hemorrhaging promotes tearing of the intima and eventually aortic dissection.

The major risk factors for FAD include high blood pressure, old age, haematoma, genetic weakening of aortic wall, cocaine use, pregnancy and diseases causing abnormal connective tissue. One study found that the average age(s) for the occurrence of dissection caused by degenerative aneurysm is 65 years and up. Dissections thought to be the result of genetic mutations appear to be more likely to occur between the ages of 40 and 60. Another study found that 20% of patients with FAD have a close relative with a history of thoracic aortic aneurysm or dissection which suggests yet another major risk factor.

Several types of right-sided aortic arch exist, the most common ones being right-sided aortic arch with aberrant left subclavian artery and the mirror-image type. The variant with aberrant left subclavian artery is associated with congenital heart disease in only a small minority of affected people. The mirror-image type of right aortic arch is very strongly associated with congenital heart disease, in most cases tetralogy of Fallot.

Supravalvular aortic stenosis is associated with genetic damage at the Elastin gene locus on chromosome 7q11.23. Fluorescent in situ hybridisation techniques have revealed that 96% of patients with Williams syndrome, where supravalvular aortic stenosis is characteristic, have a hemizygous deletion of the Elastin gene. Further studies have shown that patients with less extensive deletions featuring the Elastin gene also tend to develop supravalvular aortic stenosis

Considered part of the PTEN hamartoma tumor syndrome (PHTS), which also includes Bannayan-Riley-Ruvalcaba syndrome, Proteus syndrome, and Proteus-like syndrome, Cowden syndrome is a serious genetic disorder characterized by multiple hamartomas. Usually skin hamartomas exist, and commonly (in about 66% of cases) hamartoma of the thyroid gland exists. Additional growths can form in many parts of the body, especially in bones, CNS, the eyes, the genitourinary tract, the GI tract, and mucosa. The hamartomas themselves may cause symptoms or even death, but morbidity is more often associated with increased occurrence of malignancies, usually in the breast or thyroid.