INTRODUCTION — The primary therapy for differentiated (papillary and follicular) thyroid cancer is surgery. Considerable controversy exists about how much thyroid tissue should be removed at the initial operation, and there are no prospective randomized clinical trials to provide guidance for selection of the optimal operation.
This topic will review the rationale behind selection of the most appropriate type of operation for the treatment of differentiated thyroid cancer, the basic approaches to the operation, and management of the medical complications of surgery, particularly hypoparathyroidism. The technique of thyroidectomy and staging of thyroid cancer, as well as an overview of the management of differentiated thyroid cancer, radioiodine treatment, systemic therapy, and external radiotherapy, are discussed separately.
●(See "Thyroidectomy".)
●(See "Differentiated thyroid cancer: Clinicopathologic staging".)
●(See "Differentiated thyroid cancer: Overview of management".)
●(See "Differentiated thyroid cancer: Radioiodine treatment".)
●(See "Differentiated thyroid cancer refractory to standard treatment: Systemic therapy".)
●(See "Differentiated thyroid cancer: External beam radiotherapy".)
IMPORTANCE OF PREOPERATIVE IMAGING — We perform preoperative ultrasound evaluation of the central and lateral neck lymph nodes for all patients with malignant cytological findings on the fine-needle aspiration (FNA). Preoperative ultrasound is important for planning the surgical procedure.
Ultrasonography of the central and lateral neck identifies abnormal lymph nodes in as many as 20 to 30 percent of patients [1,2]; these ultrasound findings may alter the planned surgical procedure in up to 20 percent of patients [3,4]. However, ultrasonography can miss as many as 50 percent of the involved lymph nodes in the central neck because the overlying thyroid gland hinders adequate visualization [5].
While ultrasonography is the preferred modality for evaluation of the thyroid and cervical lymph nodes, alternative imaging modalities such as magnetic resonance imaging (MRI), computed tomography (CT) with contrast, laryngoscopy, and endoscopy may be required in patients with potentially more advanced local disease in order to accurately define the extent of tracheal, nodal, esophageal, laryngeal, or vascular involvement [6]. Additional imaging beyond routine preoperative neck ultrasonography should be obtained in patients presenting with locally advanced disease, as manifested by:
●Clinically palpable metastatic lymphadenopathy or other evidence of extensive lymph node involvement identified preoperatively, as these patients may have nodal involvement in regions inadequately evaluated with ultrasound (mediastinal, infraclavicular, retropharyngeal, or parapharyngeal lymph node chains)
●Signs or symptoms of locally invasive disease:
•Dysphagia
•Respiratory compromise
•Hemoptysis
•Rapid tumor enlargement
•Changes in voice
•Vocal cord paralysis
•Tumor fixed to surrounding structures
•Ultrasonographic evidence of macroscopic extrathyroidal extension
In these locally advanced cases, we routinely obtain preoperative CT of the neck and chest with intravenous contrast to evaluate these lymph node chains and optimize surgical planning. In such cases, the benefit of accurate surgical planning outweighs the delay in radioiodine administration that is necessary after the use of iodinated contrast. Fludeoxyglucose-positron emission tomography (FDG-PET) scanning is seldom used in preoperative surgical planning.
APPROACH TO THYROIDECTOMY
Types of procedures — There are two potential surgical approaches to differentiated thyroid cancer: total (or near-total) thyroidectomy and unilateral lobectomy and isthmusectomy. A third option, subtotal thyroidectomy, is considered to be an inadequate procedure and is not recommended.
●Total thyroidectomy – Total thyroidectomy involves removal of all thyroid tissue while attempting to identify and preserve the recurrent laryngeal nerve (RLN), the superior laryngeal nerve (SLN), and the vascular supply to the parathyroid glands.
Near-total thyroidectomy is identical except for a slightly more conservative approach to preserving the posterior thyroid capsule of the lobe contralateral to the thyroid tumor.
●Lobectomy with isthmusectomy – A unilateral lobectomy and isthmusectomy involves removal of one entire lobe and the isthmus, without entering the contralateral neck.
The difference between total and near-total thyroidectomy procedures is primarily a semantic one because most patients who undergo radioiodine imaging after total thyroidectomy have thyroid-bed uptake consistent with residual normal thyroid tissue. Whether there is a clinically important difference between total thyroidectomy and near-total thyroidectomy is uncertain. This was illustrated by the results of an analysis of 23,605 patients from the National Cancer Institute (NCI) Surveillance, Epidemiology, and End Results (SEER) database with median follow-up of 6.6 years [7]. In a multivariate analysis adjusted for prognostic variables (ie, older age, larger tumors with extrathyroidal extension), the absolute difference in 10-year overall (0.9 percent) and cause-specific (0.2 percent) survival favored total thyroidectomy, but the difference, although statistically significant, was small and of uncertain clinical significance.
If total thyroidectomy is indicated, but an experienced thyroid surgeon is unavailable, and it is impossible to refer the patient elsewhere, then the slightly more conservative "near-total" procedure should be performed. In addition, a surgeon intending to perform a total thyroidectomy for more extensive disease may choose to stop with a unilateral lobectomy and isthmusectomy if the RLN has been damaged or intentionally sacrificed during the resection of the initial lobe. The patient should subsequently be referred to a specialist for completion of thyroidectomy [8].
Subtotal thyroidectomy, in which several grams of thyroid tissue are preserved along the posterior capsule bilaterally, is an inadequate procedure for patients with thyroid cancer. It is associated with a higher complication rate if subsequent surgery is required, and we do not recommend it [9-11].
Choice of procedure
Initial surgery — The initial operative approach depends upon many factors, including the extent of the disease (eg, primary tumor size and the presence of extrathyroidal extension or lymph node metastases), the perceived need for radioiodine scanning and therapy postoperatively, the patient's age, the presence of comorbid conditions, and the skill of the surgeon. In the absence of prospective trials, conclusions regarding the optimal surgical approach are based upon retrospective analyses and expert consensus opinions [6,12].
Given access to an experienced thyroid surgeon, we suggest the following procedures for patients with intrathyroidal papillary or follicular cancer.
●Absence of extrathyroidal extension, absence of metastases (cervical lymph node or distant)
•Tumor ≤1 cm – For unilateral intrathyroidal differentiated thyroid cancer ≤1 cm, a thyroid lobectomy is the preferred approach unless there are clear indications to remove the contralateral lobe (eg, clinically evident thyroid cancer in the contralateral lobe, previous history of childhood head and neck radiation, strong family history of thyroid cancer, or imaging abnormalities that will make follow-up difficult).
•Tumor >1 to ≤4 cm – For intrathyroidal tumors >1 to ≤4 cm, the initial surgical procedure can either be a total thyroidectomy or thyroid lobectomy. Total thyroidectomy would be chosen based on patient preference, the presence of ultrasonographic abnormalities in the contralateral lobe (nodules, thyroiditis in the contralateral lobe, or nonspecific lymphadenopathy, which will make follow-up difficult), or on a decision by the treatment team that radioiodine therapy may be beneficial either as adjuvant therapy or to facilitate follow-up.
•Tumor >4 cm – It is uncommon to have a papillary thyroid cancer >4 cm without either cervical lymph node involvement or extrathyroidal extension. Therefore, most patients with tumors >4 cm undergo thyroidectomy. However, the 2024 NCCN guidelines modified the wording of their guidelines to allow for consideration of lobectomy in carefully selected patients with low risk intrathyroidal papillary thyroid cancers >4 cm [12]. In addition to absence of extrathyroidal extension and absence of metastases, low risk includes absence of a known germline mutation associated with familial thyroid cancer, absence of childhood history of head and neck irradiation, absence of aggressive histology (if core biopsy was performed).
In properly selected patients with low-risk disease, thyroid lobectomy is an acceptable alternative to total thyroidectomy based on extensive data showing low mortality, low recurrence rates, and lower surgical complication rates [6,8,12,13]. In patients with intrathyroidal tumors, retrospective analyses of databases through 2006 showed similar survival for total thyroidectomy and lobectomy [7,14-18]. Subsequently, multiple systematic reviews, meta-analyses, and large database retrospective studies comparing total thyroidectomy with thyroid lobectomy in properly selected patients with differentiated thyroid cancer confirmed similar excellent overall survival and disease-specific survival rates [19-23]. Although there is a slightly higher risk of locoregional recurrence in patients treated with thyroid lobectomy, these recurrences are effectively treated with additional surgery at the time of disease detection.
Additional support for thyroid lobectomy in patients with intrathyroidal tumors is related to:
•The marked increase in diagnosis and treatment of very-low-risk thyroid cancers
•A trend toward a risk-adapted, individual management approach in thyroid cancer
•Recommendations calling for more selective use of radioiodine as ablation or adjuvant therapy in intrathyroidal tumors (<4 cm)
•A decrease in the use of radioiodine scanning as a routine test in follow-up
•Routine use of neck ultrasonography as the primary follow-up imaging modality
•A better understanding of how serum thyroglobulin (Tg) can be used in follow-up of patients that did not undergo radioiodine ablation
A review of 194,254 patients treated between 2004 and 2019 demonstrated a statistically significant increase in the use of thyroid lobectomy for differentiated thyroid cancers in the 1 to 2 cm size range (6.8 to 18.9 percent) and in the 2 to 4 cm size range (6.6 to 16 percent) after introduction of the 2015 American Thyroid Association (ATA) guidelines [24].
●Extrathyroidal extension and/or metastases (cervical lymph node or distant), any tumor size – Patients with extrathyroidal extension or clinically apparent metastatic disease to nodes or distant sites should undergo total (or near-total) thyroidectomy [6,12,25].
In a multicenter analysis of outcomes of nearly 3000 patients with differentiated thyroid cancer, significantly worse overall survival was reported in the patients with extrathyroidal extension and/or metastases to locoregional nodes or distant sites who underwent less-than-total or near-total thyroidectomy (with risk ratios for all-cause mortality in subgroups ranging from 1.36 to 1.76) [25].
●History of childhood head and neck radiation, any tumor size – Total thyroidectomy should also be performed in all patients with thyroid cancer who have a history of exposure to ionizing radiation of the head and neck, given the high rate of tumor recurrence with lesser operations in these patients [26]. (See "Radiation-induced thyroid disease".)
●Multifocal papillary microcarcinoma (fewer than five foci) – Unilateral lobectomy and isthmusectomy is an appropriate procedure for patients whose pathology reports subsequently show multifocal papillary microcarcinomas with fewer than five foci.
●Multifocal papillary microcarcinoma (more than five foci) – When multifocal papillary cancer is appreciated preoperatively, particularly when a large number of microcarcinoma are suspected (eg, greater than five foci, especially if the foci are in the 8 to 9 mm size range), we are more likely to perform a total thyroidectomy [25,27].
For patients whose initial procedure was a lobectomy and in whom pathology shows multifocal papillary microcarcinomas with more than five foci, especially if the foci are in the 8 to 9 mm range, we typically refer patients for completion thyroidectomy.
●Indeterminate or suspicious thyroid nodules – For patients with a cytologically indeterminate nodule (Bethesda III or IV), a unilateral lobectomy and isthmusectomy is usually performed unless mutational testing suggests the nodule is likely to be benign. Because as many as 60 percent of these patients may prove to have benign disease, total thyroidectomy is usually not required as the initial procedure [28]. If the final pathologic diagnosis is cancer and if a completion thyroidectomy is needed (for example, to administer radioiodine), it can be performed without significant increased risk because the second surgery would avoid the first operative field [29,30]. This occurs most commonly in patients with follicular cancer or follicular variant papillary cancer [30].
For patients with a cytologically suspicious nodule (Bethesda V), the choice between a lobectomy and a total thyroidectomy is less clear, since the risk of malignancy may exceed 80 percent, especially if mutational testing is positive. Additional clinical characteristics and patient preference should help determine the extent of surgery. (See "Diagnostic approach to and treatment of thyroid nodules", section on 'Management'.)
Indications for intraoperative conversion to thyroidectomy — It is important for patients to understand that even if the preoperative decision is to proceed with a thyroid lobectomy, there are intraoperative findings (eg, identification of metastatic lymph nodes, invasion into surrounding structures, confirmed contralateral disease) that could necessitate immediate conversion to a total thyroidectomy. Thus, patients are encouraged to empower the surgeon to make the decision to proceed with total thyroidectomy if clinically indicated.
Indications for subsequent completion thyroidectomy — For patients in whom the initial surgery was a thyroid lobectomy, findings on the final histology examination obtained several days after lobectomy may necessitate a completion thyroidectomy in 5 to 20 percent of patients, depending on the preferences of the patient and treatment team with regard to need for radioiodine therapy, additional staging information, or highly sensitive follow-up studies [17,31-37].
Indications for completion thyroidectomy include:
●Poorly differentiated high-grade carcinoma
●Lymphatic invasion
●Vascular invasion
●Multifocal disease >1 cm
For patients with papillary thyroid cancer who are found to have incidental microscopic central neck lymph node metastasis on pathology review, we consider thyroid lobectomy to be adequate therapy [13,38]. This approach is consistent with NCCN guidance [12].
Surgical technique — Knowledge of the surgical technique of thyroidectomy allows the referring clinician to interpret operative reports and findings, understand the particular risks of thyroidectomy, and explain to the patient what lies ahead [10,11]. The technique of thyroidectomy is reviewed in detail elsewhere. (See "Thyroidectomy".)
Preservation recurrent laryngeal nerve — Identification and preservation of the RLN and SLN are the major technical challenges of this procedure (figure 1). Indications for preoperative laryngeal exam and intraoperative nerve monitoring are reviewed elsewhere. (See "Thyroidectomy", section on 'Laryngeal examination' and "Thyroidectomy", section on 'Intraoperative nerve monitoring'.)
Parathyroid glands — In addition to identifying the RLN and SLN, normal variations in the location and number of the parathyroid glands must be appreciated to avoid postoperative hypoparathyroidism (figure 2). (See "Surgical anatomy of the parathyroid glands" and "Thyroidectomy", section on 'Parathyroid preservation'.)
●Most superior parathyroid glands are located within 1 cm of the intersection of the RLN and the inferior thyroid artery, usually within the thyroid fascia. Approximately 15 percent are located within the thyroid capsule, and the remainder are located in the retropharyngeal or retroesophageal spaces.
●The location of the inferior glands is far more variable, although they are usually anterior and lateral to the recurrent nerves. They may be just below the superior glands, posterolateral to the lower pole of the thyroid; immediately inferior or posterior to the thyroid; within or below the thymus; or in the posterior mediastinum.
●The arterial supply for the parathyroid glands is usually provided by branches of the inferior thyroid artery; compromise of these vessels is the most common cause of postoperative hypoparathyroidism.
APPROACH TO LYMPH NODE DISSECTION — The indications for central and lateral compartment lymph node dissection are reviewed below. The surgical approach, intraoperative challenges, and operative complications are reviewed separately. (See "Neck dissection for differentiated thyroid cancer".)
Nomenclature — A frequently used nomenclature defines level I nodes as submental and submandibular; level II, III, and IV nodes as upper, middle, and lower jugular, respectively; level V nodes as posterior; and level VI nodes as anterior central compartment (figure 3) [39].
Therapeutic neck dissection refers to lymph node dissection when nodal disease is identified or suspected based upon clinical examination or ultrasound evaluation, whereas prophylactic dissection refers to lymph node dissection when nodal disease is not identified preoperatively.
Our approach — In patients with differentiated thyroid cancer, we perform a preoperative assessment of nodal status with ultrasound. A neck dissection for differentiated thyroid cancer (papillary and follicular) should be performed as a therapeutic procedure when nodal disease is identified or suspected based upon the clinical examination or ultrasound evaluation.
A prophylactic central neck dissection (level VI) for patients with thyroid cancer is controversial. It is not necessary for small, noninvasive papillary and most follicular cancers. However, for patients with advanced primary tumors (>4 cm and/or with extrathyroidal invasion), clinically involved lateral lymph nodes, or if the information will contribute to the planning of further therapy, we perform prophylactic central lymph node dissection. (See 'Therapeutic lymph node dissection' below and 'Prophylactic lymph node dissection' below.)
Therapeutic lymph node dissection — Therapeutic lymph node dissection should be performed if there is clinical evidence (on exam or ultrasound) of central or lateral node metastases due to the increased risk of neck recurrence and mortality [40]. This approach is consistent with the National Comprehensive Cancer Network (NCCN) and American Thyroid Association (ATA) guidelines, which recommend central and/or lateral neck dissection only in the presence of grossly positive metastases [6,12].
During the operation, the lymph nodes should be inspected, and any suspected of containing cancer should be biopsied.
●If nodes in the central compartment (level VI, the region bounded by the jugular veins, the hyoid bone, and the upper mediastinum) are found to contain cancer, dissection of all lymphatic and surrounding tissue in that compartment should be performed (figure 4).
●If any nodes in the upper, middle, or lower jugular nodal groups (levels II, III, IV) are found to contain cancer, complete dissection of nodal tissue along the jugular and carotid vessels should be done. Radical dissection, with removal of the internal jugular vein, spinal accessory nerve, and sternocleidomastoid muscle, is rarely necessary.
There is general agreement that therapeutic node dissection should be performed in patients with papillary cancer who have visibly involved nodes [6,41]. We perform lateral node dissection based upon intraoperative gross involvement or preoperative ultrasound detection [42]. Preoperative cervical ultrasound can detect clinically nonpalpable, metastatic nodes in up to 20 percent of patients with papillary cancer, including those with primary tumors <1 cm in diameter [4,43]. Lateral compartment nodes containing metastases detectable by ultrasound are associated with a shortened relapse-free survival, whereas those only found by histologic examination do not predict altered outcomes [43].
Although cervical nodal metastases are rare in patients with follicular cancer, patients with the Hürthle cell variant may have nodal disease (which predicts a worse outcome) and should have a therapeutic neck dissection if metastatic lymph nodes are identified [42].
Prophylactic lymph node dissection — We agree with the ATA guidelines, which suggest prophylactic central compartment neck dissection (ipsilateral or bilateral) for advanced primary tumors (>4 cm and/or with extrathyroidal invasion), clinically involved lateral lymph nodes, or if the information will contribute to the planning of further therapy, but is not necessary for small, noninvasive papillary and most follicular cancers [6]. There are no data to show that routine prophylactic lateral neck dissection benefits patients' long-term survival [44,45], and therefore, we do not perform this procedure.
Microscopic regional lymph node metastases of papillary cancer occur in up to 80 percent of patients. However, only approximately 35 percent have cervical or mediastinal node metastases that are detected at the time of initial surgery. Because microscopic nodal disease is rarely of clinical importance or subsequent radioiodine administration ablates these occult foci, and observational studies have not shown a clear benefit in reducing locoregional recurrence rates, many authors argue that prophylactic neck dissection of microscopic lymph node metastases that are not clinically identifiable at the time of surgery may not improve long-term outcome and could subject patients to more risk than benefit [46-49].
However, the precise role of prophylactic neck dissection for well-differentiated thyroid cancer remains controversial because in experienced hands, this procedure can be done with minimal additional risk [50], and some observational studies have suggested a survival benefit in selected patients [51-54]. Since thyroid cancers harboring the BRAF mutation have the potential to be more clinically aggressive and less responsive to radioiodine adjuvant therapy, some authors have suggested that prophylactic central neck dissection be considered for these patients [55]. However, until additional data are available demonstrating a clinical benefit to this approach, we are not advocating prophylactic neck dissection on the basis of the molecular profile of the tumor at the current time.
Others who routinely perform prophylactic central neck dissection argue that the absence of involved nodes and adverse pathological features modifies the indication for radioiodine therapy in many patients. In a retrospective study of 115 patients with papillary thyroid cancers under 2 cm (without ultrasound evidence of cervical nodes) undergoing neck dissection, 13 of 115 patients were identified (11 percent) who were expected to receive adjunctive radioiodine therapy but did not because of the surgical findings [56]. Follow-up in this study was only one year, and any benefit of avoiding radioiodine therapy has to be balanced against the risk of complications of neck dissection.
SURGERY FOR INVASIVE DISEASE — The primary tumor or local and regional metastases may invade the strap muscles, trachea, recurrent laryngeal nerves (RLNs), larynx, esophagus, thoracic duct, or carotid sheath. Careful preoperative and intraoperative evaluation, including laryngoscopy and symptom-guided imaging studies, is essential [11].
Conservative procedures, such as vertical hemilaryngectomy for unilateral laryngeal cartilage invasion or circumferential tracheal resection for subglottic invasion, may allow maintenance of function [57]. However, extensive intraluminal invasion may occasionally necessitate total laryngectomy. While attempting to preserve normal organ function is important, gross resection of all visible tumor, if possible, should be the goal of surgical intervention.
COMPLICATIONS — Thyroid surgery is associated with risk for metabolic complications, of which hypoparathyroidism is the most common, and anatomic complications, including damage to the laryngeal nerves. Both complications are more likely to occur after total thyroidectomy combined with lymph node dissection [58]. (See "Thyroidectomy", section on 'Complications'.)
Postoperative hypoparathyroidism is rare following lobectomy because a unilateral procedure avoids the contralateral neck. Similarly, although hoarseness may result from damage to one recurrent laryngeal nerve (RLN) in approximately 1 percent of cases, a unilateral procedure avoids the possibility of bilateral paralysis [59].
Hypoparathyroidism — Hypoparathyroidism is the most frequent complication of total or near-total thyroidectomy. Transient hypoparathyroidism occurs in up to 20 percent of patients after surgery for thyroid cancer [60,61], and permanent hypoparathyroidism occurs in 0.8 to 3 percent of patients after total thyroidectomy [58,60,62-64] and is more common when anatomic landmarks are displaced and obscured.
The hallmark of acute hypocalcemia is tetany, which is characterized by neuromuscular irritability. The symptoms of tetany may be mild (peri-oral numbness, paresthesias of the hands and feet, muscle cramps) or severe (carpopedal spasm, laryngospasm, and focal or generalized seizures, which must be distinguished from the generalized tonic muscle contractions that occur in severe tetany). Chvostek's and Trousseau's signs are indicative of neuromuscular irritability due to hypocalcemia. (See "Clinical manifestations of hypocalcemia", section on 'Tetany'.)
Current requirements for short hospital stays argue for early treatment of hypocalcemia. We generally use the following regimen (table 1):
●Patients with symptomatic hypocalcemia (circumoral and distal extremity paresthesias) or a serum calcium concentration below 7.8 mg/dL (2 mmol/L, with correction for any abnormality in the serum albumin concentration) should be treated with calcitriol 0.5 mcg twice daily and calcium carbonate 500 mg four times daily. For patients who absorb calcium carbonate poorly, calcium citrate may be used. Calcium glubionate is available as a liquid, although calcium carbonate can be crushed and mixed with water to form a drinkable slurry.
●Patients with more severe symptoms (muscle cramps) or a serum calcium concentration below 7.5 mg/dL (1.9 mmol/L) should also receive calcium gluconate by continuous intravenous drip for 24 to 36 hours or until the serum calcium concentration rises and is maintained above 8 mg/dL (2 mmol/L). Details on preparing the intravenous calcium solution are found elsewhere. (See "Treatment of hypocalcemia", section on 'Intravenous calcium dosing'.)
●Emergency therapy is indicated in patients with tetany, seizures, laryngospasm, or markedly prolonged QT intervals on the electrocardiogram. Treatment is initiated with the intravenous administration of one 10 mL ampule of 10 percent calcium gluconate over 5 to 10 minutes, followed by calcium gluconate by continuous intravenous drip for 24 to 36 hours or until the serum calcium concentration rises and is maintained above 8 mg/dL (2 mmol/L). (See "Treatment of hypocalcemia", section on 'Intravenous calcium dosing'.)
●If oral vitamin D and calcium carbonate cannot be tapered and then discontinued over the next two to eight weeks, the hypoparathyroidism may be permanent. Measurement of serum parathyroid hormone (PTH) concentrations when serum calcium is low can confirm the permanent need for treatment. (See "Hypoparathyroidism", section on 'Management'.)
An alternative approach is to treat all patients undergoing thyroidectomy with calcitriol and calcium carbonate starting the day before surgery, in an effort to avoid the postoperative hypocalcemia, with a plan to taper and eventually discontinue these medications over the next few weeks.
Hypoparathyroidism is reviewed in more detail separately. (See "Hypoparathyroidism", section on 'Acute hypoparathyroidism: Postsurgical'.)
Recurrent and superior laryngeal nerve injury — Occasionally, the RLN must be sacrificed intentionally due to direct tumor invasion into the nerve or surrounding tissues. As a postoperative complication, unilateral paresis of the RLN has been reported in approximately 3.9 percent of patients and bilateral in 0.2 percent [65]. However, after six months, the incidence of nerve paresis was only 1 percent, suggesting that injury may be temporary.
Endotracheal intubation or laryngeal mask airway ventilation can cause RLN injury as well as arytenoid dislocation, vocal cord edema, and other causes of postoperative hoarseness. High division of the vagus nerve near the carotid bulb will paralyze both the superior laryngeal nerve (SLN) and the RLN, resulting in both sensory and motor deficits with significant risk for aspiration. Injury to the SLN results in voice weakness or fatigue as well as changes to both voice quality and pitch. Injury to the RLN may result in paresis or paralysis of the true vocal cord to a paramedian or lateral position.
Intraoperative monitoring of RLN function may reduce this complication, but data are conflicting. Intraoperative neuromonitoring and nerve injury following thyroidectomy are reviewed in more detail separately. (See "Thyroidectomy", section on 'Nerve injury/vocal cord paresis or paralysis'.)
POSTOPERATIVE THYROID HORMONE THERAPY — After thyroid surgery, patients require postoperative thyroid hormone therapy both to replace normal hormone production and to suppress regrowth of tumor. Thyroid hormone therapy, including goals for thyroid hormone suppression, is reviewed in detail separately. (See "Differentiated thyroid cancer: Overview of management", section on 'Postoperative thyroid hormone' and "Differentiated thyroid cancer: Overview of management", section on 'Thyroid hormone suppression'.)
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Thyroid nodules and cancer".)
SUMMARY AND RECOMMENDATIONS
●Preoperative imaging – We perform preoperative ultrasound evaluation of the central and lateral neck lymph nodes for all patients with malignant cytological findings on the fine-needle aspiration (FNA) and additional imaging in patients with locally advanced disease. (See 'Importance of preoperative imaging' above.)
●Surgical options – The primary therapy for differentiated (papillary and follicular) thyroid cancer is surgery. Surgery should be performed by an experienced thyroid surgeon to minimize the risk of hypoparathyroidism and recurrent laryngeal nerve (RLN) injury.
Surgical options include total/near-total thyroidectomy or unilateral thyroid lobectomy with isthmusectomy. The initial operative approach depends upon many factors, including the extent of the disease (eg, primary tumor size and the presence of extrathyroidal extension or lymph node metastases), the perceived need for radioiodine scanning and therapy postoperatively, the patient's age, and the presence of comorbid conditions. Subtotal thyroidectomy is an inadequate procedure for patients with thyroid cancer. (See 'Types of procedures' above.)
●Choice of surgical procedure
•Absence of extrathyroidal extension, absence of metastases (cervical lymph node or distant)
-Tumor ≤1 cm – For patients with intrathyroidal unilateral differentiated thyroid cancer ≤1 cm, we suggest a thyroid lobectomy and isthmusectomy rather than total thyroidectomy (Grade 2B). The 30-year survival rate for this subgroup of patients approaches 100 percent. If there are clear indications to remove the contralateral lobe (eg, clinically evident thyroid cancer in the contralateral lobe, previous history of childhood head and neck radiation, strong family history of thyroid cancer, or imaging abnormalities that will make follow-up difficult), total thyroidectomy is preferred. (See 'Initial surgery' above.)
-Tumor >1 to ≤4 cm – For patients with intrathyroidal tumors >1 to ≤4 cm, either thyroid lobectomy or total thyroidectomy can be performed depending on the preference of the patient and the treatment team. (See 'Initial surgery' above.)
Total thyroidectomy would be chosen based on presence of ultrasonographic abnormalities in the contralateral lobe (nodules, thyroiditis in the contralateral lobe, or nonspecific lymphadenopathy, which will make follow-up difficult), or on a decision by the treatment team that radioiodine therapy may be beneficial either as adjuvant therapy or to facilitate follow-up.
If an experienced thyroid surgeon is unavailable and the patient cannot be referred elsewhere, a near-total thyroidectomy or a lobectomy may be preferable to a more complete operation complicated by bilateral nerve damage or hypoparathyroidism.
-Tumor >4 cm – It is uncommon to have a papillary thyroid cancer >4 cm without either cervical lymph node involvement or extrathyroidal extension. Therefore, most patients with tumors >4 cm undergo thyroidectomy. However, lobectomy is an option for carefully selected patients with low risk (eg, absence of extrathyroidal extension, absence of metastases, absence of a known germline mutation associated with familial thyroid cancer, absence of childhood history of head and neck irradiation) intrathyroidal papillary thyroid cancers >4 cm. (See 'Initial surgery' above.)
●Extrathyroidal extension and/or metastases – Patients with papillary or follicular cancer with extrathyroidal extension of tumor or metastases to lymph nodes or distant sites should undergo total thyroidectomy. Surgery should be performed by an experienced thyroid surgeon. (See 'Initial surgery' above.)
Because of the high risk of hypocalcemia after thyroidectomy, serum calcium concentration should be measured the evening and first morning after total thyroidectomy. Treatment of postoperative hypocalcemia should be tailored to the severity and expected duration of parathyroid deficiency (table 1). (See 'Hypoparathyroidism' above.)
●Indications for lymph node dissection – For patients with thyroid cancer with clinical evidence (on exam or ultrasound) of central or lateral node metastases, we recommend therapeutic regional lymph node dissection (Grade 1B). For patients with large primary tumors (>4 cm), high-risk features for recurrence (extrathyroidal invasion), or if the information will contribute to the planning of further therapy, we suggest prophylactic central compartment lymph node dissection (Grade 2C). Prophylactic central lymph node dissection is not necessary for small, noninvasive papillary and most follicular cancers. (See 'Approach to lymph node dissection' above.)
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