**Psammoma Bodies**

**Core Concept**
Psammoma bodies are laminated calcifications found in certain types of tumors, typically papillary thyroid carcinoma, serous ovarian cystadenocarcinoma, and meningiomas. These structures are composed of concentric layers of calcium phosphate and are formed through a process of dystrophic calcification.

**Why the Correct Answer is Right**
Psammoma bodies are a characteristic feature of papillary thyroid carcinoma, which arises from the follicular epithelium of the thyroid gland. The formation of psammoma bodies in this tumor type is thought to occur through the deposition of calcium phosphate in response to the accumulation of proteinaceous material within the tumor. This process is often associated with the presence of the BRAF V600E mutation, which is a common genetic alteration in papillary thyroid carcinoma.

**Why Each Wrong Option is Incorrect**
**Option A:** Psammoma bodies can also be seen in serous ovarian cystadenocarcinoma, a type of epithelial ovarian cancer. This option is incorrect because it is a correct association.
**Option B:** Meningiomas, a type of brain tumor, can also exhibit psammoma bodies. This option is incorrect because it is a correct association.
**Option C:** Psammoma bodies have not been consistently associated with medullary thyroid carcinoma, a type of thyroid cancer that arises from the parafollicular cells (C cells). This option is correct because it is a tumor type where psammoma bodies are not typically seen.

**Clinical Pearl / High-Yield Fact**
Psammoma bodies are a valuable diagnostic clue in the histopathological examination of thyroid and ovarian tumors. Their presence can help distinguish papillary thyroid carcinoma from other types of thyroid cancer and serous ovarian cystadenocarcinoma from other types of ovarian cancer.

**Correct Answer: C. Medullary thyroid carcinoma.