**Core Concept**
Hurthle cells are a type of epithelial cell characterized by their large size, abundant eosinophilic cytoplasm, and often, a large, central nucleus. They are typically seen in the thyroid gland, specifically in conditions that lead to cellular response and neoplastic transformation.

**Why the Correct Answer is Right**
Hurthle cells are associated with Hashimoto thyroiditis, a chronic autoimmune condition where the immune system attacks the thyroid gland. The presence of Hurthle cells is a hallmark of this condition, often seen in the context of lymphocytic infiltration and fibrosis. The mechanism behind Hurthle cell formation is thought to involve the transformation of follicular epithelial cells in response to chronic inflammation and autoimmune stimulation.

**Why Each Wrong Option is Incorrect**
**Option A:** Hurthle cells are not typically seen in thyroiditis, which is a more general term encompassing a range of conditions, including Hashimoto's and Graves'. While some forms of thyroiditis may involve Hurthle cell-like changes, this is not the primary condition associated with these cells.
**Option B:** Hurthle cells are not a characteristic feature of papillary thyroid carcinoma, a type of thyroid cancer. While Hurthle cell carcinoma is a distinct entity, it is not the primary condition associated with Hurthle cells.
**Option C:** Hurthle cells are not specifically associated with medullary thyroid carcinoma, which arises from the parafollicular (C) cells of the thyroid gland.

**Clinical Pearl / High-Yield Fact**
Hurthle cells are often seen in the context of autoimmune thyroiditis, specifically Hashimoto thyroiditis, and are characterized by their distinctive large size and abundant eosinophilic cytoplasm.

**Correct Answer:** D.