**Core Concept**
Papillary thyroid carcinoma is a type of well-differentiated thyroid cancer that typically presents as a solitary nodule in the thyroid gland. The treatment of choice for papillary thyroid carcinoma is surgical resection, often in the form of a total thyroidectomy.

**Why the Correct Answer is Right**
The American Thyroid Association recommends total thyroidectomy as the treatment of choice for papillary thyroid carcinoma, especially in patients with tumors larger than 1 cm. This is because total thyroidectomy offers a higher chance of cure and reduces the risk of recurrence compared to lobectomy. The thyroid gland is then replaced with levothyroxine to maintain euthyroidism.

**Why Each Wrong Option is Incorrect**
**Option A:** Lobectomy is generally not recommended as the primary treatment for papillary thyroid carcinoma due to the risk of recurrence and the need for lifelong follow-up.
**Option B:** Radioactive iodine therapy is typically reserved for patients with high-risk features, such as lymph node metastases or distant metastases, and not as the initial treatment for papillary thyroid carcinoma.
**Option C:** External beam radiation therapy is not typically used as a primary treatment for papillary thyroid carcinoma, as the cancer is usually radiosensitive and can be effectively treated with surgery and radioactive iodine.

**Clinical Pearl / High-Yield Fact**
Papillary thyroid carcinoma often presents with lymph node metastases, even in the absence of palpable cervical nodes. Therefore, it is essential to perform a thorough neck dissection during surgery to ensure complete removal of the cancer.

**Correct Answer: D. Total thyroidectomy.**