Open Total Thyroidectomy and Central Neck Dissection for Papillary Thyroid Cancer in the Setting of Hashimoto's Thyroiditis

Abstract

Papillary thyroid cancer is the most common type of thyroid malignancy. While prognosis is overall favorable, many patients present with clinically positive lymph nodes, most commonly in the central neck compartment. Total thyroidectomy with central lymph node dissection is the treatment of choice in these patients. 

Keywords

Papillary thyroid cancer; PTC; total thyroidectomy; central lymph node dissection; CLND.

Case Overview

Background

The incidence of thyroid cancer has increased substantially over time with an estimated incidence of 14.42 cases per 100,000 person-years.¹ Most thyroid cancer cases are differentiated thyroid cancer, with papillary thyroid cancer (PTC) comprising 70–85% of all thyroid cancers.² PTC occurs three times more frequently in women as compared to men and most commonly affects people in their third to fifth decades.³ Established risk factors for PTC include exposure to ionizing radiation as well as family history.

Overall survival for PTC is excellent, with a 10-year disease-specific survival of 96%,⁴ even though a significant proportion of patients have lymph node metastasis in the central and/or lateral lymph nodes at presentation.⁵ Only 3–5% develop distant metastasis, most commonly to lung and bone.² Aggressive variants such as diffuse sclerosing variant, tall cell variant, columnar cell variant, and hobnail variant, comprise a very small percentage of PTC cases and may be associated with higher rates of recurrence, metastasis, and resistance to radioactive iodine.⁶ 

Focused History of the Patient

The patient is a 30-year-old female with no prior medical history who presented to her primary care physician with two weeks of left neck swelling in the setting of pharyngitis. She underwent thyroid function studies which were normal and thyroid ultrasound, which demonstrated bilateral thyroid nodules. The largest nodule in the left thyroid lobe met criteria for biopsy. She underwent fine needle aspiration (FNA) biopsy, which resulted as papillary carcinoma, and therefore she was referred for surgical evaluation.

Physical Exam

The thyroid exam is often a routine component of primary care physical exam and may serve to diagnose otherwise asymptomatic cancer. For a patient presenting with neck swelling, exam of the neck, including inspection and palpation of the thyroid gland and cervical lymph nodes, is the first step in evaluation. Approximately 30–40% of thyroid cancer diagnoses are detected by palpation,⁷ with the remainder being detected on incidental or surveillance imaging. 

When our patient presented, she was found to have thyromegaly on exam by her primary care physician. On referral to an endocrinologist almost two weeks later, she was found to have a thyroid of normal size without palpable nodules or lymph nodes. Her neck was non-tender and she otherwise appeared well. 

Imaging

Neck ultrasonography is the imaging modality of choice for the thyroid gland, with excellent evaluation of thyroid nodular disease as well as cervical lymphadenopathy. Nodule characteristics that are associated with higher rate of malignancy include solid composition, hypoechogenicity, microcalcifications, irregular margins and taller-than-wide shape. The Thyroid Imaging Reporting & Data System (TIRADS) scoring system uses these features in addition to nodule size to provide standardized indications for biopsy. Depending on the setting of the ultrasound, FNA biopsy can be performed concurrently if indicated. 

Our patient underwent ultrasound shortly after her initial presentation, which demonstrated a small right thyroid nodule and a larger left thyroid nodule, measuring 8 mm and 23 mm in largest diameter, respectively. The left thyroid nodule was further characterized as mixed cystic and solid and hypoechoic with smooth margins and punctate echogenic foci. These features yielded a TIRADS score of 4, which is an indication for biopsy for nodules greater than 1.5 cm in size. She therefore underwent FNA biopsy, which returned as thyroid carcinoma. The ultrasound further demonstrated a cluster of lymph nodes inferior to the left thyroid lobe.

Natural History

Some patients who are found to have very low-risk PTC can undergo active surveillance rather than definitive treatment, which has provided some insight into the natural history of these lesions. Initial data from Japan on the safety of surveillance protocols for PTC less than 1 cm in size demonstrated that 10–15% of nodules grew 3 mm or more within 5 years of surveillance.⁸ A study of 291 patients with PTC less than 1.5 cm without additional suspicious features demonstrated that cumulatively 12.1% of patients experienced at least 3 mm growth within 5 years of active surveillance.⁹ No patients in this study developed regional or distant metastasis during surveillance.⁹ Prognostic models have demonstrated overall high survival rates for patients with untreated early-stage PTC with 86% and 66% 10-year survival for patients with stage I and II disease, respectively.¹⁰ In this same model, patients with untreated mid- to advanced-stage PTC fared progressively poorer with increasing disease stage.¹⁰

Options for Treatment

As discussed previously, some patients with very low-risk PTC can be considered for active surveillance to evaluate interval growth. Aside from this select cohort, the gold standard treatment for PTC is thyroidectomy. The extent of surgery, thyroid lobectomy versus total thyroidectomy, is determined based on tumor size, nodal status, the presence of metastatic disease and coexistent contralateral thyroid disease. Patients should undergo concurrent lymph node dissection of involved compartments if there is preoperative concern or confirmation of nodal disease. If lobectomy is chosen as the initial operation, the patient should be counseled that they may need to undergo completion lobectomy based on the surgical pathology. Features that would indicate a completion lobectomy include tumor size larger than 4 cm, extrathyroidal extension or vascular invasion, positive margins, macroscopic multifocal disease, and macroscopic nodal disease.¹¹

Postoperative radioactive iodine (RAI) is indicated based on clinicopathologic features. In general, patients with extrathyroidal extension or vascular invasion, bulky or more than 5 positive lymph nodes, significant N1b disease, high-grade carcinoma or distant metastasis are candidates for adjuvant RAI.

Rationale for Treatment

Our patient presented with a confirmed left thyroid PTC, concurrent small right thyroid nodule and prominent nodes inferior to the left thyroid lobe. Although subcentimeter, her right thyroid nodule demonstrated some suspicious characteristics including being hypoechoic with ill-defined margins and punctate echogenic foci. Therefore, a shared decision was made to proceed with total thyroidectomy with central lymph node dissection (CLND). 

Discussion

While papillary thyroid cancer has an overall favorable prognosis, up to 35% of patients present with clinically positive nodal disease, most commonly in the central neck compartment.¹² It is further estimated that up to 80% of patients with clinically negative lymph nodes may harbor microscopic metastatic disease.¹² The central neck compartment is comprised of level VI lymph nodes, bounded anatomically by the hyoid bone superiorly, the sternal notch inferiorly and the carotid sheaths laterally, and level VII lymph nodes, which are associated with the brachiocephalic and innominate artery. 

Patients with clinically positive or suspicious central nodes based on physical exam, preoperative ultrasound or biopsy, or intraoperative inspection should undergo therapeutic CLND with comprehensive clearance of all nodal tissue. As with our current case, patients with concurrent Hashimoto’s thyroiditis often have benign enlarged nodes that confound clinical assessment. The role of prophylactic CLND is controversial. Some surgeons perform prophylactic CLND routinely for all PTC, while most consensus guidelines advocate that it may be considered for patients with larger (T3/T4) tumors, tumors with high-risk features or the presence of positive lateral neck nodes.¹³ There is no clear evidence on rate of recurrence or oncologic benefit of performing CLND, though it may help to better stage patients with implications for adjuvant RAI.¹³ CLND has been associated with increased risk of hypoparathyroidism and recurrent laryngeal nerve injury and therefore these risks must be considered when deciding to perform CLND in addition to thyroidectomy.^14,15 

Our patient was observed in the postoperative care unit for several hours and then discharged home the same day as surgery. Her parathyroid hormone level was checked in the postoperative care unit and found to be normal which is important for safe same-day discharge in these cases.¹⁶ Her pathology revealed a 2.1-cm classical type papillary thyroid carcinoma with overall favorable features. She was found to have 4 of 6 positive central lymph nodes with the largest metastatic deposit measured at 1 mm and no extranodal extension. Given these features, she did not require any additional treatment in addition to surgery.

Equipment

Nerveana nerve monitor. Stryker Ethicon Harmonic scalpel. 

Disclosures

The authors have no disclosures to report. 

Statement of Consent

The patient referred to in this video article has given their informed consent to be filmed and is aware that information and images will be published online.