Inflammatory myofibroblastic tumour is a lesional pattern of inflammatory pseudotumour, as plasma cell granuloma. It is abbreviated IMT.

The symptoms depend on the specific location of the tumour, which can be anywhere in the body.

The relation between dietary fat and atherosclerosis is controversial. Writing in "Science", Gary Taubes detailed that political considerations played into the recommendations of government bodies. The USDA, in its food pyramid, promotes a diet of about 64% carbohydrates from total calories. The American Heart Association, the American Diabetes Association and the National Cholesterol Education Program make similar recommendations. In contrast, Prof Walter Willett (Harvard School of Public Health, PI of the second Nurses' Health Study) recommends much higher levels of fat, especially of monounsaturated and polyunsaturated fat. These differing views reach a consensus, though, against consumption of trans fats.

The role of dietary oxidized fats/lipid peroxidation (rancid fats) in humans is not clear.

Laboratory animals fed rancid fats develop atherosclerosis. Rats fed DHA-containing oils experienced marked disruptions to their antioxidant systems, and accumulated significant amounts of phospholipid hydroperoxide in their blood, livers and kidneys.

Rabbits fed atherogenic diets containing various oils were found to undergo the greatest amount of oxidative susceptibility of LDL via polyunsaturated oils. In another study, rabbits fed heated soybean oil "grossly induced atherosclerosis and marked liver damage were histologically and clinically demonstrated." However, Fred Kummerow claims that it is not dietary cholesterol, but oxysterols, or oxidized cholesterols, from fried foods and smoking, that are the culprit.

Rancid fats and oils taste very bad even in small amounts, so people avoid eating them.

It is very difficult to measure or estimate the actual human consumption of these substances. Highly unsaturated omega-3 rich oils such as fish oil are being sold in pill form so that the taste of oxidized or rancid fat is not apparent. The health food industry's dietary supplements are self regulated and outside of FDA regulations. To properly protect unsaturated fats from oxidation, it is best to keep them cool and in oxygen free environments.

The atherosclerotic process is not fully understood. Atherosclerosis is initiated by inflammatory processes in the endothelial cells of the vessel wall associated with retained low-density lipoprotein (LDL) particles. This retention may be a cause, an effect, or both, of the underlying inflammatory process.

The presence of the plaque induces the muscle cells of the blood vessel to stretch, compensating for the additional bulk, and the endothelial lining thickens, increasing the separation between the plaque and lumen. This somewhat offsets the narrowing caused by the growth of the plaque, but it causes the wall to stiffen and become less compliant to stretching with each heart beat.

Patients can lower their risk for vulnerable plaque rupture in the same ways that they can cut their heart attack risk: Optimize lipoprotein patterns, keep blood glucose levels low normal (see HbA1c), stay slender, eat a proper diet, quit smoking, and maintain a regular exercise program. Researchers also think that obesity and diabetes may be tied to high levels of C-reactive protein.

A vulnerable plaque is a kind of atheromatous plaque – a collection of white blood cells (primarily macrophages) and lipids (including cholesterol) in the wall of an artery – that is particularly unstable and prone to produce sudden major problems such as a heart attack or stroke.

The defining characteristics of a vulnerable plaque include but are not limited to: a thin fibrous cap, large lipid-rich necrotic core, increased plaque inflammation, positive vascular remodeling, increased vasa-vasorum neovascularization, and intra-plaque hemorrhage. These characteristics together with the usual hemodynamic pulsating expansion during systole and elastic recoil contraction during diastole contribute to a high mechanical stress zone on the fibrous cap of the atheroma, making it prone to rupture. Increased hemodynamic stress, e.g. increased blood pressure, especially pulse pressure (systolic blood pressure vs. diastolic blood pressure difference), correlates with increased rates of major cardiovascular events associated with exercise, especially exercise beyond levels the individual does routinely. This video , examining autopsy specimens from an actual heart attack resulting in sudden death, shows the sequence. These videos, and , illustrate the sequence of events and why, though the underlying process develops over decades, the symptoms are usually of sudden onset.

Generally an atheroma becomes vulnerable if it grows more rapidly and has a thin cover separating it from the bloodstream inside the arterial lumen. Tearing of the cover is called "plaque rupture".

Repeated atheroma rupture and healing is one of the mechanisms, perhaps the dominant one, that creates artery stenosis.

An atheroma is a reversible accumulation of degenerative material in the inner layer of an artery wall. The material consists of mostly macrophage cells, or debris, containing lipids, calcium and a variable amount of fibrous connective tissue. The accumulated material forms a swelling in the artery wall, which may intrude into the channel of the artery, narrowing it and restricting blood flow. Atheroma occurs in atherosclerosis, which is one of the three subtypes of arteriosclerosis (which are atherosclerosis, Monckeberg's arteriosclerosis and arteriolosclerosis).

In the context of heart or artery matters, atheromata are commonly referred to as atheromatous plaques. It is an unhealthy condition found in most humans.

Veins do not develop atheromata, because they are not subjected to the same hemodynamic pressure that arteries are, unless surgically moved to function as an artery, as in bypass surgery. The accumulation (swelling) is always in the tunica intima, between the endothelium lining and the smooth muscle middle layer of the artery wall. While the early stages, based on gross appearance, have traditionally been termed fatty streaks by pathologists, they are not composed of fat cells but of accumulations of white blood cells, especially macrophages, that have taken up oxidized low-density lipoprotein (LDL). After they accumulate large amounts of cytoplasmic membranes (with associated high cholesterol content) they are called foam cells. When foam cells die, their contents are released, which attracts more macrophages and creates an extracellular lipid core near the center to inner surface of each atherosclerotic plaque. Conversely, the outer, older portions of the plaque become more calcified, less metabolically active and more physically stiff over time.

For most people, the first symptoms result from atheroma progression within the heart arteries, most commonly resulting in a heart attack and ensuing debility. However, the heart arteries, because (a) they are small (from about 5 mm down to microscopic), (b) they are hidden deep within the chest and (c) they never stop moving, have been a difficult target organ to track, especially clinically in individuals who are still asymptomatic. Additionally, all mass-applied clinical strategies focus on both (a) minimal cost and (b) the overall safety of the procedure. Therefore, existing diagnostic strategies for detecting atheroma and tracking response to treatment have been extremely limited. The methods most commonly relied upon, patient symptoms and cardiac stress testing, do not detect any symptoms of the problem until atheromatous disease is very advanced because arteries enlarge, not constrict in response to increasing atheroma. It is plaque ruptures, producing debris and clots which obstruct blood flow downstream, sometimes also locally (as seen on angiograms), which reduce/stop blood flow. Yet these events occur suddenly and are not revealed in advance by either stress testing, stress tests or angiograms.