Open Thyroidectomy - Clinical Tree

Introduction

Although thyroid disease has been recognized for centuries, consistently accepted techniques of thyroid surgery date back approximately 100 years. With a combined mortality of 40% from hemorrhage and sepsis, thyroidectomy was banned by the French Academy of Medicine in 1850. However, with the advent of antiseptic technique, vascular ligation, and precise capsular dissection, Theodor Kocher reduced the perioperative mortality rate to less than 1% in 900 cases for benign goiter in 1895. He was awarded the Nobel Prize in Medicine in 1909 for his contributions to thyroid surgery. Crile, Lahey, and the Mayo brothers founded their internationally famous private clinics largely based on their ability to perform thyroid surgery safely.

Thyroid nodules are found by palpation in 4% to 7% of subjects and by imaging in 30% to 67% of the population. While nonmalignant thyroid abnormalities are quite common, 5% to 20% of nodules may contain malignancy on excision. Studies suggest that 33% of subjects have thyroid cancer on autopsy, and that approximately 50% of the population may have microscopic thyroid cancer.

Carcinoma of the thyroid accounts for approximately 3.8% of cancers in the United States, with an estimated 62,450 new cases in 2015 and 75% occurring in women. It is currently the fifth leading new cancer diagnosis in women and is projected to overtake colorectal cancer as the fourth leading cancer diagnosis overall in the United States by 2030. Although the incidence of thyroid cancer has risen in recent years, perhaps due to the increased use of ultrasound, its mortality rate has remained stable with a 5-year survival of approximately 98%, accounting for 0.3% of all cancer deaths in 2015.

Key Operative Learning Points

1.
Identification and continued observation of the recurrent laryngeal nerve is the best way to avoid injury to the nerve.
2.
Skeletonize the superior pedicle and ligate close to the thyroid gland to avoid injury to the superior laryngeal nerve and parathyroids.
3.
Identify and lateralize the parathyroid glands with their blood supply.
4.
Careful placement of the incision and protection of skin edges promote optimal cosmetic results.

Preoperative Period

History

1.
History of present illness
- a.
  Evaluate for onset, duration, change in size, growth rate, and pain.
  - 1)
    Asymptomatic nodules are often found on imaging.
  - 2)
    Rapid growth of a new or previously stable nodule is concerning for malignancy.
  - 3)
    Pain is not commonly associated with thyroid cancer and may represent thyroiditis or hemorrhage into a benign nodule.
- b.
  Compressive symptoms: Shortness of breath and dyspnea (especially with lying flat), persistent dysphagia
- c.
  Invasive symptoms: Hemoptysis, fixation of the overlying skin, or hoarseness from paralysis of the vocal cord
- d.
  Hyper or hypothyroid symptoms: Palpitations, weight change, fatigue, anxiety, sleep disturbance, or menstrual changes
2.
Risk factors for thyroid cancer
- a.
  Age
  - 1)
    Less than 20: ∼20% risk of malignancy in a solitary nodule
  - 2)
    20 to 40: 5% to 10% risk of malignancy in a solitary nodule
  - 3)
    Peak in women 45 to 50, men 65 to 70
- b.
  Gender: There is a triple prevalence in women, but thyroid nodules in men are more likely to be malignant.
- c.
  Two or more first-degree relatives with a history of thyroid cancer
- d.
  Exposure to low dose radiation to the neck
3.
Past medical history
- a.
  Hashimoto’s thyroiditis
  - 1)
    Nodules are 30% more likely to contain papillary thyroid cancer.
  - 2)
    Increased risk of lymphoma
- b.
  Consider multiple endocrine neoplasia type 2 (MEN-2) and medullary thyroid carcinoma in patients with pheochromocytoma, hyperparathyroidism, marfanoid habitus, and/or mucosal neurofibromas.
- c.
  Gardner syndrome (polyposis coli) and Cowden disease are associated with thyroid cancer.

Physical Examination

1.
Complete examination of the head and neck.
- a.
  Palpate thyroid for enlargement and nodules.
  - 1)
    Note size, shape, firmness, movement with swallowing, fixation to skin, or underlying structures.
- b.
  Palpate neck for lymphadenopathy.
- c.
  Listen for hoarseness, stridor.
2.
Direct or indirect laryngoscopy
- a.
  This is essential in detecting vocal cord paralysis.
- b.
  The voice may be normal despite a paralyzed vocal cord.

Laboratory Studies

1.
Thyroid stimulating hormone (TSH)
- a.
  Initial study of choice to rule out hypo or hyperthyroidism
2.
Thyroglobulin (Tg)
- a.
  Cannot reliably differentiate between benign and malignant thyroid disease
3.
Calcitonin
- a.
  Usually not recommended unless patient has a family history of medullary thyroid carcinoma or MEN-2, or biopsy shows medullary thyroid carcinoma

Imaging

1.
Ultrasound (US)
- a.
  Thyroid US with attention to central compartment should be performed in all patients with a thyroid nodule, even when found on computed tomography (CT).
- b.
  Provides details on size, consistency, other nodules, and associated cervical lymphadenopathy
- c.
  Useful for serial monitoring of nodules and lymph nodes
- d.
  Findings associated with malignancy include
  - 1)
    Complex nodules
  - 2)
    Irregular margins
  - 3)
    Increased nodular vascularity
- e.
  Microcalcifications are associated with markedly increased risk of malignancy, while cystic and spongiform appearance may be associated with benign lesions.
2.
CT and magnetic resonance imaging (MRI)
- a.
  Generally not needed
- b.
  Can be helpful for
  - 1)
    Substernal extension
  - 2)
    Cervical and mediastinal lymphadenopathy
  - 3)
    Invasion of surrounding structures such as trachea and esophagus
  - 4)
    Metastasis to distant body sites
- c.
  Use of iodinated contrast may preclude the use of radioactive iodine (RAI) for 1 to 3 months.
3.
Radionuclide scanning
- a.
  Usually performed with ¹²³ I or technetium 99m ( ^99m Tc) sestamibi
- b.
  Incidence of malignancy is 4% in “hot” nodules and 10% to 15% in “cold” nodules.
- c.
  Not routinely performed unless TSH level indicates hyperthyroidism
  - 1)
    If hyperfunctioning nodule, no cytologic evaluation necessary and consideration for ablative radioiodine
  - 2)
    If hypofunctioning, may indicate malignancy
  - 3)
    Most cancers are isometabolic

Fine Needle Aspiration

1.
Best initial diagnostic test
- a.
  Minimally invasive, safe, and cost effective
- b.
  Sensitivity 65% to 98%; specificity 72% to 100%
- c.
  US guidance increases accuracy and success of fine needle aspiration (FNA)
2.
Suspicious cervical lymph nodes should undergo FNA in addition to that of thyroid nodules.
3.
When multiple nodules are present, the largest and/or most sonographically suspicious should preferentially be biopsied.
- a.
  Multiple nodules may need to be biopsied to increase diagnostic yield.
4.
Bethesda classification of thyroid cytopathology
- a.
  I: Nondiagnostic, 1% to 4% risk of malignancy
- b.
  II: Benign, 0% to 3% risk.
- c.
  III: Atypia of undetermined significance (AUS) or follicular lesion of undetermined significance (FLUS), 5% to 15% risk.
  - 1)
    This is a gray zone where repeat FNA, observation with serial US, and surgery are all potential options.
- d.
  IV: Follicular neoplasm, 15% to 30% risk
- e.
  V: Suspicious for malignancy, 60% to 75% risk
- f.
  VI: Malignant, 97% to 99% risk

Molecular Biomarkers

1.
Newer studies introduced to increase accuracy of FNA and better characterize the risk of malignancy, especially in indeterminate cytology, AUS, and FLUS lesions. These markers may
- a.
  Reduce unnecessary surgery for benign lesions
- b.
  Reduce completion thyroidectomy by guiding initial use of total thyroidectomy
- c.
  Provide prognostic information
2.
Examples: BRAF, RAS, TIMP1, RET/PTC, Pax8-PPARγ, galectin-3, cytokeratin, microRNA, gene sequencing
3.
Uncertain evidence regarding efficacy and utility

Indications

Total Thyroidectomy

1.
Differentiated thyroid carcinoma if one or more of the following:
- a.
  Tumor greater than 4 cm
  - 1)
    Between 1 and 4 cm: Option of lobectomy or total thyroidectomy
- b.
  Gross extrathyroidal extension
- c.
  Contralateral thyroid nodule or cervical/distant metastasis
- d.
  Multinodular goiter with radiation exposure to head and neck
- e.
  First degree family members with thyroid cancer
2.
Medullary thyroid carcinoma
3.
Anaplastic thyroid carcinoma, depending on resectability
4.
Bilateral indeterminate nodules
5.
Multinodular goiter causing compressive symptoms
6.
Medically refractory Grave’s disease or hyperthyroidism

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