**Psammoma Bodies Seen in A/E**

**Core Concept**
Psammoma bodies are small, concentrically laminated calcifications found in certain types of tumors. They are a characteristic feature of papillary thyroid carcinoma, serous ovarian carcinomas, and meningiomas. Psammoma bodies are formed through the deposition of calcium salts in the extracellular matrix.

**Why the Correct Answer is Right**
Psammoma bodies are composed of concentric layers of calcium phosphate, which are deposited in a concentric pattern around a central core. This process is thought to be mediated by the enzyme alkaline phosphatase, which is present in the tumor cells. The presence of psammoma bodies is a diagnostic feature of papillary thyroid carcinoma, particularly in fine-needle aspiration biopsies.

**Why Each Wrong Option is Incorrect**
**Option A:** Psammoma bodies are not typically seen in renal cell carcinoma, which is a different type of tumor altogether. Renal cell carcinoma is characterized by clear cell morphology and is often associated with other features such as tubulopapillary architecture and the presence of foamy macrophages.
**Option B:** Psammoma bodies are not typically seen in squamous cell carcinoma, which is a different type of tumor altogether. Squamous cell carcinoma is characterized by its pleomorphic appearance and is often associated with other features such as keratinization and the presence of desmoplastic stroma.
**Option C:** Psammoma bodies are not typically seen in medullary thyroid carcinoma, which is a different type of thyroid cancer. Medullary thyroid carcinoma is characterized by its spindle cell morphology and is often associated with other features such as amyloid deposition and the presence of calcitonin-producing cells.
**Option D:** Psammoma bodies are not typically seen in follicular thyroid carcinoma, which is a different type of thyroid cancer. Follicular thyroid carcinoma is characterized by its follicular morphology and is often associated with other features such as capsular invasion and vascular invasion.

**Clinical Pearl / High-Yield Fact**
Psammoma bodies are a "must-see" feature in thyroid fine-needle aspiration biopsies, as their presence is highly suggestive of papillary thyroid carcinoma. However, it's worth noting that psammoma bodies can also be seen in other types of tumors, such as meningiomas and serous ovarian carcinomas.

**Correct Answer: C. Medullary thyroid carcinoma.**