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A woman in her early 30s presents to a clinic after being referred for assessment of a large mass on the right side of her neck, explaining that it developed about 3 to 4 weeks earlier. She notes she has not felt fatigued or had any problems with swallowing, hoarseness, or coughing.

On physical examination, clinicians identify a nodule in the right lobe of her thyroid that they estimate is about 1.5 cm. Ultrasound reveals a solid nodule of 1.3×1.2 cm, with irregular borders.

Lab tests show the patient has a low thyrotropin level of 0.005 mU/L, and high triiodothyronine of 5.03 nmol/L. Thyroid scintigraphy indicates significantly elevated uptake in the right lobe of the thyroid compared with the left. Compared with normal values of 7-35%, the 24-hour thyroid uptake is 53%; her thyroid autoantibody titers are not tested.

Clinicians recommend that she undergo thyroid lobectomy with possible excision of the whole thyroid, which she agrees to. Surgeons remove the right lobe of the thyroid and send the frozen sectioning of the removed specimen to pathology during the operation.

Pathology's analysis identifies a 1.2 cm papillary thyroid carcinoma, oncocytic type; there is one lymph node involved, but no evidence of extranodal or vascular invasion. At this time, surgeons remove the left lobe of the thyroid.

The patient recovers from surgery within 24 hours without any notable symptoms such as hoarseness, dysphagia, or hypocalcemia. She notes an intention to become pregnant in the near future, so clinicians defer the radioactive iodine ablation therapy.

At a follow-up visit 1 month after surgery, the patient says she has not had any further symptoms such as hoarseness, muscle aches or cramps, or sensory changes in her toes or fingertips, that might raise suspicion of hypoparathyroidism. She is currently taking levothyroxine for thyroid hormone replacement, and shows no signs of disease recurrence.

The final pathology report identifies an oncocytic variant of papillary carcinoma involving the lymph node, but there is no extranodal or extrathyroidal extension. The background parenchyma of the right thyroid lobe shows diffuse hyperplasia and focal calcifications but no evidence of lymphocytosis.

The left thyroid lobe shows focal nodular hyperplasia but is otherwise normal. Genetic testing of the specimen is not performed.

Discussion

Clinicians reporting this of a patient who presents with a unilateral hyperfunctioning thyroid nodule – identified post-surgery as cancerous – caution that while it is rare, the possibility of cancer should not be ruled out completely in these patients.

The authors note that of the approximately 5% of women and 1% of men in iodine-sufficient communities who present with palpable nodules, approximately 7% to 15% will develop thyroid cancer, with 90% either the papillary or follicular type.

Due to the rarity of cancers that develop in a hyperfunctioning "hot" nodule versus a hypofunctioning "cold" nodule, "if [a malignancy] is found that corresponds to the [hot] nodule in question, no cytologic evaluation is necessary," according to the American Thyroid Association's most recent (2015) for management of adult patients with thyroid nodules and differentiated thyroid cancer.

Ultrasound is recommended to confirm the location and characteristics of a thyroid nodule, but even in the presence of suspicious ultrasonography findings such as irregular borders that would warrant further testing in a cold nodule, current guidelines do not recommend fine-needle aspiration and cytology in patients with a solitary thyroid nodule and hyperthyroidism.

Papillary thyroid carcinoma spreads quickly to local lymph nodes, but surgery is usually curative, the case authors note, citing a 10-year survival rate of 97% after surgery and improved prognosis associated with female sex and younger age.

In a multivariate of 5,897 patients with papillary thyroid carcinoma, age over 55 had the strongest prognostic value (HR 8.33), compared with distant metastasis (HR 6.06), tumor size over 4.0 cm (HR 2.27), and clinical node metastasis greater than 3.0 cm (HR 2.64) (P<0.0001 for all variables).

After thyroidectomy, hyperthyroidism is very rare (approximately 1%) in patients with a hot nodule, and thus there is no need for further radioactive , the case authors explain.

Their patient's mass was identified as the oncocytic variant of papillary thyroid carcinoma, which accounts for approximately 5% of papillary thyroid carcinomas. A found no reports of this carcinoma in a hyperfunctioning nodule.

This case is also rare since oncocytic papillary thyroid carcinoma typically presents in older patients (average age 5 years older than for other papillary carcinoma subtypes) and with a larger tumor size (2.8 cm compared with 1.5 cm for other papillary carcinomas), the authors note.

They emphasize that although most autonomous thyroid nodules are noncancerous, it is imperative to inform patients of the possibility of malignancy. Furthermore, despite the fact that fine-needle aspiration is not recommended for these patients, clinicians should have a low threshold for operative management in order to prevent complications of an untreated malignancy. Cancer cannot be ruled out without pathological study of the specimen.

Conclusion

The case authors conclude that thyroid nodules are a common cause of a unilateral neck mass, and although most are noncancerous, early detection and treatment of a thyroid malignancy can be curative and can prevent metastasis to lymph nodes. In addition, the higher recurrence rate of oncocytic papillary carcinoma compared with other types of papillary carcinoma should encourage physicians to pursue radioactive iodine ablation therapy after surgery, when feasible, to decrease the risk of recurrent disease.

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