BACKGROUND Thyroid nodules are a common cause of neck swelling in clinical practice, even in iodine-sufficient communities. Most nodules are benign, but malignancy cannot be excluded. The majority of thyroid cancers occur in nonfunctioning nodules, but in rare cases they can present as an autonomous nodule. Papillary carcinoma, the most common type of thyroid malignancy, typically spreads quickly to local lymph nodes; however, current guidelines do not recommend biopsy of autonomous thyroid nodules. Early detection and surgical intervention can be curative in many of these cases. CASE REPORT This present case involved a woman in her early 30s who presented with an enlarging neck mass. Ultrasound demonstrated a unilateral right thyroid mass, and blood work showed triiodothyronine thyrotoxicosis. Thyroid scintigraphy was performed and showed unilateral increased uptake on the right side. The patient was treated initially with a thyroid lobectomy. Intraoperative frozen sectioning of the removed specimen showed papillary thyroid carcinoma, and a total thyroidectomy was performed. Radioactive iodine ablation therapy was not done, but given the patient's history and risk factors, recurrence of her disease is unlikely. CONCLUSIONS The vast majority of autonomous thyroid nodules are noncancerous. However, patients should be informed of the possibility of malignancy, and cancer should be ruled out clinically. Papillary thyroid carcinoma accounts for the majority of tumors in both hot and cold nodules. However, the oncocytic subtype seen in the patient in this report is less common, presents a higher risk of recurrence, and typically occurs in older patients. Thyroidectomy is usually curative for patients with papillary thyroid carcinoma.