**Question:** All of the thyroid tumor arises from follicular epithelial cell except:

**Core Concept:** Thyroid tumors are either benign or malignant and can arise from various cell types within the thyroid gland. The primary cell types involved in thyroid tumors include:

1. Follicular epithelial cells: These cells form the thyroid follicles and are responsible for producing thyroid hormones.
2. C cells (parafollicular cells): These cells produce calcitonin hormone, which is involved in calcium regulation.
3. Hurthle cells (Hürthle cells): These cells are a variant of follicular cells and are often associated with larger tumors.

**Why the Correct Answer is Right:** The correct answer, **D**, refers to the C cell tumors, which are distinct from the follicular epithelial cells that form the majority of thyroid tumors. C cell tumors, also known as medullary thyroid carcinoma (MTC), are relatively rare and characterized by the production of calcitonin, a hormone involved in calcium regulation.

**Why Each Wrong Option is Incorrect:**

A. This option is incorrect because it refers to parafollicular cells (C cells), which are responsible for calcitonin production, and are indeed involved in thyroid tumors, as explained above.
B. This option is incorrect because Hurthle cells are a variant of follicular epithelial cells and are not specific to thyroid tumors.
C. This option is incorrect because it refers to medullary thyroid carcinoma (MTC), which is a subtype of thyroid tumors and involves parafollicular cells (C cells).

**Clinical Pearl:** Although Hurthle cells are a variant of follicular cells, they are not specific to thyroid tumors. Thyroid tumors are primarily classified based on the cell type involved, with the majority being follicular epithelial cells, followed by Hurthle cells and then parafollicular cells (C cells). This distinction is crucial for understanding the pathogenesis, clinical presentation, and treatment options for thyroid tumors.