## Core Concept
Atheromatous plaques, also known as atherosclerotic plaques, are lesions that form in the arteries due to the accumulation of lipids, inflammatory cells, and fibrous elements. They are characteristic of atherosclerosis, a condition that can lead to cardiovascular diseases.

## Why the Correct Answer is Right
The composition of an atheromatous plaque typically includes a lipid core rich in cholesterol and cholesterol esters, covered by a fibrous cap composed of smooth muscle cells, collagen, and other extracellular matrix components. The plaque also contains inflammatory cells such as macrophages and T lymphocytes.

## Why Each Wrong Option is Incorrect
- **Option A:** This option would be incorrect because atheromatous plaques do contain lipid-laden macrophages (foam cells) and cholesterol crystals.
- **Option B:** This option is incorrect as well because the fibrous cap of an atheromatous plaque is indeed composed of smooth muscle cells and extracellular matrix, including collagen.
- **Option C:** This option would also be incorrect since atheromatous plaques do contain inflammatory cells, including macrophages and T lymphocytes.

## Clinical Pearl / High-Yield Fact
A key clinical pearl is that the vulnerability of an atheromatous plaque to rupture is more related to its composition (e.g., a large lipid core, thin fibrous cap) than its size. Plaque rupture can lead to acute occlusion of the artery, resulting in conditions such as myocardial infarction or stroke.

## Correct Answer: D.