**Core Concept**
Psammoma bodies are small, round, or oval structures composed of concentric layers of calcium salts, often seen in certain types of tumors. They are a type of dystrophic calcification, which occurs in abnormal or necrotic tissue.

**Why the Correct Answer is Right**
Psammoma bodies are typically associated with mucinous adenocarcinomas, such as papillary thyroid carcinoma, serous ovarian cystadenocarcinoma, and meningiomas. The formation of psammoma bodies is thought to be a result of the deposition of calcium salts in areas of tissue necrosis or inflammation.

* They are formed through the accumulation of calcium phosphate or calcium carbonate in a concentric, lamellar pattern.
* This process is often seen in tumors with a papillary or glandular architecture.
* Psammoma bodies are usually multiple and may be found in a variety of locations within the tumor.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not correct because psammoma bodies are not typically associated with vascular calcification, which involves the deposition of calcium salts in the walls of blood vessels.
**Option B:** This option is incorrect because dystrophic calcification is a broader category that includes psammoma bodies, but it also encompasses other types of calcification, such as calcification in areas of tissue damage or necrosis.
**Option C:** This option is not correct because psammoma bodies are not typically associated with metastatic calcification, which occurs in the presence of hypercalcemia or other metabolic disorders.

**Clinical Pearl / High-Yield Fact**
Psammoma bodies are often seen in papillary thyroid carcinoma, and their presence can be a helpful diagnostic clue in this condition. They may also be found in other types of tumors, such as meningiomas and serous ovarian cystadenocarcinomas.

**Correct Answer:** D. Dystrophic calcification.