Introduction
Thyroid nodules are a common clinical problem, diagnosed by palpation on clinical examination in approximately 5% of women and 1% of men in Western society. Their presence requires evaluation to exclude thyroid cancer, the incidence of which is 15% in at-risk groups. In recent decades, the incidence of thyroid cancer has nearly tripled from 4.9 per 100,000 in 1975 to 14.3 per 100,000 in 2009. Today, it is currently the 10th most common cancer among men and women in the United States, according to the Centers for Disease Control. The National Cancer Institute’s surveillance, epidemiology, and end results (SEER) Program estimates that there will be 62,450 new cases of thyroid cancer in 2015, accounting for 3.8% of all new cancer diagnoses but only 0.3% of all cancer deaths. The increased incidence is partially attributed to the increasing use of high-resolution ultrasound in the evaluation of benign thyroid disease and solitary thyroid nodules as well as the discovery of “incidentalomas” on high-resolution computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) scans performed for other indications. In recent years, increasingly strict guidelines have been created to prevent overtreatment. There has also been a trend toward development of less invasive techniques in order to prevent morbidity in young patients with benign and low-risk papillary thyroid cancer (PTC).
In the 1990s, surgeons in Japan and Italy pioneered the development of endoscopic surgery for both benign and malignant thyroid pathology. This was driven by patient demand for either a smaller cervical scar or no scar, instead of the 8-cm incision originally described by Kocher. Since the first minimally invasive approach, various techniques have been described in the literature ( Table 79.1 ).
| Minimally invasive—mini-incision |
| Video-assisted transcervical endoscopic |
| Completely closed endoscopic |
| Transcervical approach |
| Axillary approach |
| Anterior chest approach |
| Breast approach |
The technique now known as minimally invasive video-assisted thyroidectomy (MIVAT), which has demonstrated widely reproducible results, will be the focus of this chapter. First and best described by Miccoli in 1999 for the treatment of benign thyroid disease, this technique has been expanded to include solitary nodules, low-to-intermediate risk malignancy, and central compartment neck metastases. Groups in the United States have tested its efficacy and safety, while expanding indications to include previous, relative contraindications such as patients with high body-mass index, thyroiditis, prior neck surgery, larger nodules, goiters, and completion lobectomies.
Key Operative Learning Points
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Careful patient selection is necessary for safe and expedient MIVAT surgery. Ideal candidates for MIVAT have nodules less than 3.5 cm and a thyroid gland volume less than 25 mL.
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Subplatysmal flaps are unnecessary and create dead space for seroma formation.
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Two assistants are needed: one to hold the retractors and expose the superior pole and tracheoesophageal groove and another to hold the endoscope during dissection of the superior pole, parathyroid glands, and the recurrent laryngeal nerve.
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Use of the harmonic scalpel for superior and inferior pole vessels can significantly reduce operative times.
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Conversion to open thyroidectomy (OT) should be performed for posterior nodules that prevent visualization of the recurrent laryngeal nerve (RLN), large glands that cannot be delivered through the incision, or excessive bleeding that prevents safe identification of the RLN.
Preoperative Period
Ideal candidates for MIVAT include patients with asymptomatic solitary nodules or patients with low-to-intermediate risk well-differentiated thyroid cancer and account for about 10% of all patients referred for thyroidectomy. Careful patient selection is necessary in the preoperative evaluation for MIVAT, especially for the novice surgeon. Clinical evaluation of any patient with a mass in the thyroid gland begins with a careful history and physical examination. The history, physical examination, and workup should help the surgeon exclude patients with the absolute and relative contraindications to this surgical technique, according to the surgeon skill set.
History
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History of present illness
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Presentation: How and when was the thyroid nodule discovered?
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Has it been biopsied under ultrasound?
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Does the patient have any symptoms of hyper- or hypothyroidism?
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Does the patient have hoarseness, dyspnea, dysphagia, or aspiration?
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Has the patient noticed any masses in his or her neck?
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Has the patient noticed progressively enlarging nodules?
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Past medical history
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Has the patient been diagnosed with hyper- or hypothyroidism?
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Does he or she have other autoimmune disease, such as Grave’s disease or acute Hashimoto’s thyroiditis?
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Has the patient had prior radiation of the head and neck?
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Has the patient been exposed to ionizing radiation?
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Does the patient have a history of previous cardiac stent, deep vein thrombosis, or pulmonary embolization requiring anticoagulation or antiplatelet therapy?
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Is the patient pregnant?
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Past surgical history
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Has the patient had any previous thyroid surgery or parathyroid surgery?
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Has the patient had other prior neck surgery?
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Family history
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Is there a family history of thyroid cancer or cancer-related syndrome?
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Is there a family history of thyroid disease?
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Is there a presence of familial bleeding disorders?
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Is there a family history of hyperthermia or acetylcholinesterase deficiency with any previous anesthesia?
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Medications
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Is the patient taking thyroid hormone replacements?
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Is the patient on antiplatelet therapy or anticoagulation?
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Physical Examination
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Voice
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Assess the quality of voice; is it coarse or breathy?
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Breathing
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Does the patient have stridor?
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Thyroid gland
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Assess the size of the nodule and its mobility on swallowing.
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Assess the mobility of the overlying tissues.
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Neck
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Palpate deeply to detect any cervical lymphadenopathy that would suggest metastatic disease, as this would be a contraindication to MIVAT and would require OT with neck dissection.
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Examine the neck in extension in order to detect any substernal extension that might require OT.
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Flexible laryngoscopy
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Preoperative paresis or paralysis suggests invasive cancer that should be treated with open techniques.
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Identification of contralateral paralysis is also crucial in patients who are to undergo completion lobectomy.
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Imaging
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Ultrasound and ultrasound-guided fine-needle aspiration biopsy (US-FNAB)
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Ultrasound can detect additional suspicious nodules (solid or hypoechoic nodules with irregular margins, microcalcifications, and/or taller than wide shape, as well as evidence of soft tissue invasion or extrathyroidal extension), hypervascularity associated with thyroiditis, large thyroid volume, or substernal extension that may contraindicate MIVAT.
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Ultrasonography of the neck to evaluate lateral lymph nodes for cervical metastases is indicated for all patients being considered for MIVAT. Those patients with lateral metastases should have OT and selective neck dissection.
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CT/MRI neck
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Patients are often referred for evaluation of a thyroid nodule after incidental discovery on other imaging. For those cases where CT or MRI leads to detection of the nodule, no further imaging of the neck is necessary to look for metastatic cancer.
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PET/CT
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The incidence of focally, fluorodeoxyglucose-avid (FDG-avid) thyroid nodules on PET-CT performed for other means is 1% to 2%. Because there is a 35% risk of cancer in such cases, hemi-thyroidectomy is indicated for pathologic tissue analysis.
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Indications
The main indications for MIVAT in the literature include benign lesions, indeterminate nodules, and low-risk papillary thyroid carcinoma.
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Small thyroid nodules (25 to 30 mm in diameter)
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Thyroid gland volume (about 20 cm )
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No evidence of acute thyroiditis
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Specific groups
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Children
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Thyroid masses in children are most commonly well-differentiated papillary thyroid carcinoma (WDPTC) and medullary thyroid carcinoma (MTC).
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Fine-needle aspiration biopsy (FNAB)–proven, WDPTC is an indication for MIVAT.
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FNAB-proven MTC is a relative contraindication, as the patient requires total thyroidectomy with central compartment and possible lateral neck dissections. Prophylactic treatment of pediatric patients with familial disease and positive RET (rearranged during transfection) proto-oncogene testing, who display no evidence of thyroid nodules or neck metastases on exam or imaging, can be treated by MIVAT alone in experienced hands. An advantage of MIVAT in these two patient populations is the significant reduction in postoperative pain, as compared with standard thyroidectomy.
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Patients with a history of exposure to ionizing radiation
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Patient’s with occupational or environmental radiation exposures are considered to be in the high-risk category and are more likely to have multifocal cancer requiring total thyroidectomy. A third of abnormalities in the thyroid gland in patients with a history of radiotherapy will be malignant. These patients are perfect candidates for MIVAT.
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Patients with a history of therapeutic head and neck radiation should undergo OT, as the radiation creates scarring, radiation changes and an adverse surgical field with increased risk for bleeding.
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Geriatric patients
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This group can undergo MIVAT safely with low morbidity, as with younger patients. However, MIVAT has been shown to require longer anesthesia times as compared with conventional techniques in inexperienced hands. Therefore only experienced surgeons, with comparable operative times to conventional open approaches, should offer MIVAT for patients in the geriatric age group.
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Contraindications
As centers have become more facile with MIVAT, the indications have expanded and the contraindications have been revised. For example, many groups have proven that larger nodules, nodules in patients with Hashimoto’s thyroiditis, Grave’s disease, prior neck surgery (as in completion thyroidectomy), and central compartment lymph node metastases requiring central neck dissection are no longer contraindications, but should still remain relative contraindications in less than experienced hands.
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Absolute contraindications include thyroid disease requiring OT.
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Large multinodular goiters
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Substernal thyroid nodules or goiters
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Revision thyroidectomy
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Prior ipsilateral neck surgery or external beam radiation to the neck
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Biopsy proven MTC
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Presence of lateral lymph node metastases
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Relative contraindications include conditions that would make minimally invasive approaches more difficult and therefore increase morbidity.
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Active thyroiditis
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Grave’s disease
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Adverse anatomic aspects (short neck in the obese patient)
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Nodules greater than 4 cm
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Completion thyroidectomy
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Central compartment metastases
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Preoperative Preparation
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Thyroid function tests
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Preoperative thyroid-stimulating hormone (TSH) levels with reflexive triiodothyronine (T 3 ) and thyroxine (T 4 ) testing to ensure the euthyroid state and avoid thyroid storm.
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Subnormal TSH levels require a radioactive iodine scan to diagnose a possible benign hyperfunctioning adenoma that can be medically treated.
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Serum thyroglobulin
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Thyroglobulin levels are not routinely indicated in the preoperative workup of nodules and low-risk cancer, as they can be elevated in many types of thyroid disease.
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Antibodies
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Antithyroglobulin antibody, antithyroid peroxidase antibody, and thyroid stimulating immunoglobulin can rule in or rule out thyroiditis, which is a relative contraindication to MIVAT. This may be particularly helpful to the novice surgeon and discourage his or her use of MIVAT, due to the higher likelihood of intraoperative bleeding and less favorable conditions for identification and preservation of the RLNs and parathyroid glands.
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FNAB
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FNAB should be performed on thyroid nodules greater than 1 cm and suspicious cervical lymph nodes and sent for cytologic analysis according to the Bethesda Guidelines for Cytologic Evaluation and Reporting.
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FNAB may diagnose atypia, a follicular lesion, or a Hürthle cell lesion, in which case one might perform a minimally invasive thyroid lobectomy for diagnosis and risk stratification.
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Molecular testing
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Testing for various mutations known to be associated with a high-risk of malignancy has been performed on FNAB specimens, allowing surgeons to be more selective about performing diagnostic lobectomy for Bethesda III and IV lesions using minimally invasive techniques.
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