A 58-yrs-old presents with increased “fullness” in her neck. Examination finds non tender diffuse enlargement of her thyroid gland. Clinically she is euthyroid. Sections from her thyroid gland reveal numerous, mainly enlarged follicles, most of which are filled with abundant colloid material. There are areas of fibrosis, hemorrhage, and cystic degeneration. No papillary structures are identified and neither colloid scalloping nor Huhle cells are present. Most likely diagnosis is?

**Core Concept**
The patient's presentation of a diffuse, non-tender thyroid gland enlargement in a euthyroid state points towards a condition that affects the thyroid gland's architecture and function, likely due to chronic stimulation or autoimmune processes.

**Why the Correct Answer is Right**
The presence of numerous, enlarged follicles filled with abundant colloid material, along with areas of fibrosis, hemorrhage, and cystic degeneration, is characteristic of a condition known as **Adenomatous Goiter**. This condition is often seen in the context of long-standing thyroid stimulation, which can be due to thyroid-stimulating hormone (TSH) secretion from a pituitary adenoma or other TSH-secreting tumors. The absence of papillary structures, colloid scalloping, or Hürthle cells helps rule out other conditions like papillary thyroid carcinoma, colloid goiter, or Hürthle cell adenoma.

**Why Each Wrong Option is Incorrect**
**Option A:** This option might be considering a subacute thyroiditis, which typically presents with pain and inflammation of the thyroid gland, not a diffuse enlargement in a euthyroid state.

**Option B:** **Colloid Goiter** is characterized by a diffuse thyroid gland enlargement with colloid scalloping and Hürthle cells, which are not present in this patient.

**Option C:** **Papillary Thyroid Carcinoma** typically presents with papillary structures, colloid scalloping, and Hürthle cells, which are not seen in this patient.

**Option D:** **Hürthle Cell Adenoma** is a type of thyroid adenoma that consists of Hürthle cells, which are not present in this patient.

**Clinical Pearl / High-Yield Fact**
A key feature of Adenomatous Goiter is its association with long-standing thyroid stimulation, which can lead to a range of complications, including thyroid nodules, adenomas, and even thyroid cancer.

**Correct Answer:** B.

✓ Correct Answer: D. Multinodular goiter