22: Thyroid Flashcards
Which type of thyroid cancer is associated with each of the below characteristics?
- Tumor arises from parafollicular C cells
- Pathology reveals psammoma bodies and Orphan Annie nuclei
- Pathology shows amyloid deposition
- Tumor secretes calcitonin
- Prognosis based on local invasion rather than stage
- Tumor arises from parafollicular C cells: Medullary thryoid carcinoma
- Pathology reveals psammoma bodies and Orphan Annie nuclei: Papillary thyroid cancer
- Pathology shows amyloid deposition: Medullary thryoid carcinoma
- Tumor secretes calcitonin: Medullary thryoid carcinoma (may be useful to monitor calcitonin levels for disease recurrence)
- Prognosis based on local invasion rather than stage: Papillary thyroid carcinoma
What is the best time to perform a thyroidectomy on a pregnant patient?
2nd trimester
[This has the lowest risk of teratogenic events and premature labor.]
What are the expected lab values (high or low) in Graves’ disease?
- TSH
- T3
- T4
- LATS
- 123I uptake (thyroid scan)
- TSH: Decreased
- T3: Increased
- T4: Increased
- LATS: Increased
- 123I uptake (thyroid scan): Diffusely increased
What are the 3 thyroid veins and to where do they drain?
- Superior thyroid vein: Drains into the internal jugular vein
- Middle thyroid vein: Drains into the internal jugular vein
- Inferior thyroid vein: Drains into the innominate vein
What do parafollicular C cells produce?
Calcitonin
What is the most common cause of hypothyroidism in adults and what is the pathogenesis of that cause?
- Hashimoto’s disease
- Caused by both humeral and cell-mediated autoimmune disease (microsomal and thyroglobulin antibodies)
[Goiter occurs secondary to lack of organification of trapped iodide inside the thyroid gland. It can cause thyrotoxicosis in the early stages of the disease.]
What is the treatment approach to papillary or follicular cell thyroid cancer with metastases?
Total thyroidectomy followed by 131I 4-6 weeks after surgery
[Total thyroidectomy needs to be performed first to facilitate uptake of 131I to the metastatic lesions, otherwise it will all get absorbed by the thyroid gland.]
What is the treatment for Hashimoto’s disease?
- Thyroxine is first line therapy
- Partial thyroidectomy if continues to grow despite thyroxine therapy, if nodules appear, or if symptoms of compression occur
[Frequently, no surgery is necessary for Hashimoto’s disease.]
What is the treatment for a toxic multinodular goiter?
- Most consider surgery (subtotal or total thyroidectomy) the preferred initial treatment
- Trial of 131I should be considered, especially in the elderly and frail
[If compression or a suspicious nodule is present then surgery is the necessary treatment.]
What is the appropriate next in step working up a patient with an asymptomatic thyroid nodule with indeterminant findings on fine needle aspiration?
Radionuclide study
[UpToDate: The initial evaluation in all patients with a thyroid nodule (discovered either by palpation or incidentally noted on a radiologic procedure, such as carotid ultrasonography, neck computed tomography [CT], or positron emission tomography [PET]) includes a history, physical examination, neck ultrasonography, and measurement of serum thyroid-stimulating hormone (TSH).
Thyroid scintigraphy should be performed in patients with a subnormal serum TSH concentration.
If the serum TSH concentration is normal or elevated and the nodule meets sonographic criteria for sampling (table 3), palpation or ultrasound-guided fine needle aspiration (FNA) biopsy should be performed (algorithm 1). FNA biopsy is the most accurate method for evaluating thyroid nodules and selecting patients for thyroid surgery. Nodules that do not meet sonographic criteria for FNA should be monitored. The frequency of evaluation depends upon the sonographic features of the nodules.
Solid hypoechoic nodules and nodules with suspicious sonographic appearance (irregular margins, microcalcifications, taller than wide shape, rim calcifications, or evidence of extrathyroidal extension) should be biopsied when ≥1 cm (as determined by largest dimension). Nodules with sonographic appearance suggesting a low risk for thyroid cancer can be biopsied when larger (≥1.5 to 2 cm). Spongiform nodules ≥2 cm could also be evaluated by FNA, although observation without FNA is an alternative option.
FNA biopsy of thyroid nodules is commonly performed under ultrasound guidance. Ultrasound-guided FNA biopsy should be performed for nonpalpable nodules and for nodules that are technically difficult to aspirate using palpation methods alone, such as predominantly cystic or posteriorly located nodules. In patients with large nodules (>4 cm), ultrasound-guided FNA directed at several areas within the nodule may reduce the risk of a false negative biopsy.
Where available, we suggest using an mRNA classifier system (gene expresser classifier), mutational analysis (using a broad next-generation sequencing assay with an expanded panel of point mutations and gene fusions), or combined testing for further evaluating FNA aspirates with indeterminate cytology (follicular lesion/atypia of undetermined significance [FLUS/AUS]) or follicular neoplasm.]
What is the appropriate treatment for a patient with an asymptomatic thyroid nodule and the following finding on fine needle aspiration?
- Follicular cells
- Thyroid cancer
- Cyst fluid
- Colloid tissue
- Normal thyroid tissue
- Follicular cells: Lobectomy (10% cancer risk)
- Thyroid cancer: Thyroidectomy or lobectomy (further treatment dependent on cancer type and stage)
- Cyst fluid: Drain fluid (lobectomy if it recurs or is bloody)
- Colloid tissue: Thyroxine (lobectomy if it enlarges)
- Normal thyroid tissue: Monitor (PTU and 131I if symptomatic)
Colloid tissue on FNA is most likely a colloid goiter with a low chance (< 1%) of malignancy.]
[UpToDate: For patients with FLUS or AUS (nodules with atypical cells or nodules with both macrofollicular and microfollicular features), we perform repeat FNA after a three to six-month interval or earlier. If repeat aspirates continue to show FLUS/AUS and thyroid scintigraphy does not show an autonomous nodule, we perform molecular testing (as for follicular neoplasm immediately below). If molecular testing is unavailable, we suggest surgical resection if repeat aspirates continue to show atypical cells (Grade 2C). For patients with nodules that are greater than 50% macrofollicular, we suggest monitoring, unless they are clinically suspicious or present in patients with a higher risk of cancer (Grade 2C).
For patients with nonautonomous (cold) follicular neoplasms (microfollicular adenomas), we send the FNA aspirate for molecular testing (if available) using a gene expresser classifier or mutational analysis with an expanded panel of point mutations and gene fusions or combined testing. If molecular testing is not available, we suggest diagnostic lobectomy rather than observation (Grade 2B). In the absence of capsular or vascular invasion (on surgical histology), the lesion is classified as a benign adenoma and no further treatment is required. For patients whose surgical histology shows follicular thyroid cancer (or follicular variant papillary thyroid cancer), completion thyroidectomy may be necessary.
For patients with indeterminate FNA cytology who have a benign molecular pattern on molecular testing, we suggest observation (Grade 2C). However, the decision to observe a patient with a benign profile should be reassessed as more data become available. Diagnostic lobectomy remains an alternative option for patients with a benign molecular pattern, depending upon the nodule’s clinical characteristics and patient preference. For patients with a suspicious molecular pattern using these techniques, diagnostic lobectomy or total thyroidectomy is indicated.
Patients with cytology suggesting cancer or suspicious for cancer should be referred for surgery.
For patients with nondiagnostic palpation or ultrasound-guided biopsies, we perform repeat FNA using ultrasound-guidance. For patients with solid nodules and nondiagnostic cytology after repeated biopsies, we typically perform an ultrasound-guided core needle biopsy. Careful clinical follow-up, repeat FNA biopsy, and surgical resection are alternative options. For cytologically nondiagnostic nodules that are predominately cystic, we suggest careful clinical follow-up with ultrasound monitoring rather than surgical resection (Grade 2C).]
What are the below characteristics of the superior laryngeal nerve?
- Provides motor innervation to what?
- Runs where in relation to the thyroid lobes?
- Tracks close to which artery?
- Injury results in what?
- Provides motor innervation to what? Cricothyroid muscle
- Runs where in relation to the thyroid lobes? Lateral
- Tracks close to which artery? Superior thyroid artery
- Injury results in what? Loss of voice projection and voice fatigability
What is the treatment for a patient with an asymptomatic thyroid nodule with indeterminant findings on fine needle aspiration and the following finding on radionuclide study?
- Hot nodule
- Cold nodule
- Hot nodule: Monitor (PTU and 131I if symptomatic)
- Cold nodule: Lobectomy (more likely malignant than a hot nodule)
[UpToDate: For patients with FLUS or AUS (nodules with atypical cells or nodules with both macrofollicular and microfollicular features), we perform repeat FNA after a three to six-month interval or earlier. If repeat aspirates continue to show FLUS/AUS and thyroid scintigraphy does not show an autonomous nodule, we perform molecular testing (as for follicular neoplasm immediately below). If molecular testing is unavailable, we suggest surgical resection if repeat aspirates continue to show atypical cells (Grade 2C). For patients with nodules that are greater than 50% macrofollicular, we suggest monitoring, unless they are clinically suspicious or present in patients with a higher risk of cancer (Grade 2C).
For patients with nonautonomous (cold) follicular neoplasms (microfollicular adenomas), we send the FNA aspirate for molecular testing (if available) using a gene expresser classifier or mutational analysis with an expanded panel of point mutations and gene fusions or combined testing. If molecular testing is not available, we suggest diagnostic lobectomy rather than observation (Grade 2B). In the absence of capsular or vascular invasion (on surgical histology), the lesion is classified as a benign adenoma and no further treatment is required. For patients whose surgical histology shows follicular thyroid cancer (or follicular variant papillary thyroid cancer), completion thyroidectomy may be necessary.
For patients with indeterminate FNA cytology who have a benign molecular pattern on molecular testing, we suggest observation (Grade 2C). However, the decision to observe a patient with a benign profile should be reassessed as more data become available. Diagnostic lobectomy remains an alternative option for patients with a benign molecular pattern, depending upon the nodule’s clinical characteristics and patient preference. For patients with a suspicious molecular pattern using these techniques, diagnostic lobectomy or total thyroidectomy is indicated.
Patients with cytology suggesting cancer or suspicious for cancer should be referred for surgery.
For patients with nondiagnostic palpation or ultrasound-guided biopsies, we perform repeat FNA using ultrasound-guidance. For patients with solid nodules and nondiagnostic cytology after repeated biopsies, we typically perform an ultrasound-guided core needle biopsy. Careful clinical follow-up, repeat FNA biopsy, and surgical resection are alternative options. For cytologically nondiagnostic nodules that are predominately cystic, we suggest careful clinical follow-up with ultrasound monitoring rather than surgical resection (Grade 2C).]
What are the following characterstics of thyroid cancer?
- Most common type of thyroid cancer
- Least aggressive type of thyroid cancer
- Second least aggressive type of thyroid cancer
- Second most aggressive type of thyroid cancer
- Most aggressive type of thyroid cancer
- Risk of malignancy with follicular cells on thyroid FNA
- Most common type of thyroid cancer: Papillary
- Least aggressive type of thyroid cancer: Papillary (95% 5-year survival)
- Second least aggressive type of thyroid cancer: Follicular (70% 5-year survival)
- Second most aggressive type of thyroid cancer: Medullary (50% 5-year survival)
- Most aggressive type of thyroid cancer: Anaplastic (0% 5-year survival)
- Risk of malignancy with follicular cells on thyroid FNA: 5-10% risk of malignancy (FNA is unable to differentiate between follicular cell adenoma, follicular cell hyperplasia, and follicular cell cancer)
- What is the mechanism of action of propylthiouracil (PTU) and methimazole?
- What is are the side effects of propylthiouracil (PTU)?
- What is are the side effects of methimazole?
- Mechanism of action of propylthiouracil (PTU) and methimazole: Inhibition of peroxidases and prevention of iodine-tyrosine coupling
- Side effects of propylthiouracil (PTU): Aplastic anemia, agranulocytosis (rare)
- Side effects of methimazole: Cretinism in newborns (crosses placenta), aplastic anemia, and agranulocytosis (rare)
[UpToDate: In addition to intellectual disability, cretinism is accompanied by other neurologic and somatic defects. This has led to cretinism being subdivided into neurologic and myxedematous types:
- Neurologic cretinism is characterized by intellectual disability, deaf mutism, gait disturbances, and spasticity but not hypothyroidism. It is thought to result from hypothyroidism in the mother during early pregnancy but a euthyroid state postnatally due to adequate iodine intake in the newborn.
- Myxedematous cretinism is characterized by intellectual disability, short stature, and hypothyroidism. It is thought to result from iodine deficiency and thyroid injury predominantly late in pregnancy and continuing after birth.
These two syndromes overlap considerably, and attributing them to specific developmental periods is undoubtedly overly simplistic. Both can be prevented by adequate maternal and infant iodine intake.]
What are the following characteristics of thyroglobulin?
- What is the T4:T3 ratio?
- Which is the more active form?
- Where is most T3 produced?
- T4:T3 ratio: 15:1
- More active form: T3
- T3 production: Peripheral conversion of T4 to T3 by deiodinases
[Deiodinases separate iodine from tyrosine.]
What must be removed during resection of a thyroglossal duct syst (Sistrunk procedure)?
Midportion or all of the hyoid bone
[Thyroglossal duct cysts should be resected because they are susceptible to infection and may be premalignant.]
What are the below characteristics of the recurrent laryngeal nerve?
- Provides motor innervation to what?
- Runs where in relation to the thyroid lobes?
- Tracks close to which artery?
- Injury results in what?
- Provides motor innervation to what? All of the larynx except the cricothyroid muscle
- Runs where in relation to the thyroid lobes? Posterior to thyroid lobes in the tracheoesophageal groove
- Tracks close to which artery? Inferior thyroid artery (variable)
- Injury results in what? Hoarseness, bilateral injury can result in airway obstruction requiring emergency tracheostomy
[UpToDate: A non-recurrent RLN may be present in nearly 1% of patients. When present, the nerve will course directly from the vagus nerve to the trachea.
Rarely, the right inferior laryngeal nerve may not recur and instead crosses transversely from the vagus nerve and behind the common carotid artery; in almost all instances, it enters the larynx at the usual level. Non-recurrence of the inferior laryngeal nerve results from a vascular anomaly during embryonic development of the aortic arches in which the fourth vascular arch and right dorsal aorta involute, causing the aberrant development of arterial structures on the right, including the lack of an innominate artery and the passage of the subclavian artery behind the esophagus.
A non-recurrent left inferior laryngeal nerve would require a right aortic arch associated with situs inversus and is exceedingly rare.]
What is this mass?
Substernal goiter
[UpToDate: The most common symptom in patients with obstructive cervical or substernal goiter is exertional dyspnea, which is present in 30% to 60% of cases. This symptom usually occurs when the tracheal diameter is under 8 mm.
Bilateral thyroid lobe enlargement, especially if the goiter extends posterior to the trachea, may cause either compression or concentric narrowing of the trachea or compression of the esophagus or jugular veins. With some goiters, there is growth of one or both lobes through the thoracic inlet into the thoracic cavity, which can result in obstruction of any of the structures in the inlet. Such goiters are referred to as substernal (image 1A-B).
Patients with obstructive symptoms from a cervical or substernal goiter require removal or ablation of the thyroid.
For patients with obstructive goiter, we suggest surgery rather than radioiodine (Grade 2C). The reduction in thyroid volume with radioiodine is only moderate, and there are theoretical concerns that radioiodine could acutely worsen obstruction or a missed malignancy. However, radioiodine therapy is an option for patients with obstructive symptoms who are poor surgical candidates.
For asymptomatic patients with normal flow-volume loops whose goiters end at the level of the brachiocephalic vein or higher, we suggest observation rather than surgery (Grade 2C). We monitor such patients with serial computed tomography (CT) scans, initially after one year, and if stable, at increasing intervals (eg, two years later, then three years, then five years).
Recommendations for asymptomatic patients with goiters that extend below the level of the brachiocephalic vein are controversial. The author of this topic suggests surgical excision for most patients except older patients and those who are poor operative candidates, while other experts suggest observation of asymptomatic patients. All patients requiring surgery for substernal goiter should be referred to experienced thyroid surgeons in high-volume centers to minimize complication rates.
For most patients undergoing surgery, we suggest a total or near-total thyroidectomy rather than subtotal thyroidectomy, to minimize the risk of recurrent goiter (Grade 2C).]
What is the Tubercle of Zuckerkandl and why is it left behind in a subtotal thyroidectomy?
- The Tubercle of Zuckerkandl is the most lateral, posterior extension of thyroid tissue
- Left behind with subtotal thyroidectomy because of the proximity to the recurrent laryngeal nerve (Rotate it medially to find the recurrent laryngeal nerve)
What is the correct approach to an asymptomatic thyroid nodule with normal thyroid function tests?
Fine needle aspiration is the best initial test
[90% of thyroid nodules are benign. There is a female predominance.]
[UpToDate: The initial evaluation in all patients with a thyroid nodule (discovered either by palpation or incidentally noted on a radiologic procedure, such as carotid ultrasonography, neck computed tomography [CT], or positron emission tomography [PET]) includes a history, physical examination, neck ultrasonography, and measurement of serum thyroid-stimulating hormone (TSH).
Thyroid scintigraphy should be performed in patients with a subnormal serum TSH concentration.
If the serum TSH concentration is normal or elevated and the nodule meets sonographic criteria for sampling (table 3), palpation or ultrasound-guided fine needle aspiration (FNA) biopsy should be performed (algorithm 1). FNA biopsy is the most accurate method for evaluating thyroid nodules and selecting patients for thyroid surgery. Nodules that do not meet sonographic criteria for FNA should be monitored. The frequency of evaluation depends upon the sonographic features of the nodules.
Solid hypoechoic nodules and nodules with suspicious sonographic appearance (irregular margins, microcalcifications, taller than wide shape, rim calcifications, or evidence of extrathyroidal extension) should be biopsied when ≥1 cm (as determined by largest dimension). Nodules with sonographic appearance suggesting a low risk for thyroid cancer can be biopsied when larger (≥1.5 to 2 cm). Spongiform nodules ≥2 cm could also be evaluated by FNA, although observation without FNA is an alternative option.
FNA biopsy of thyroid nodules is commonly performed under ultrasound guidance. Ultrasound-guided FNA biopsy should be performed for nonpalpable nodules and for nodules that are technically difficult to aspirate using palpation methods alone, such as predominantly cystic or posteriorly located nodules. In patients with large nodules (>4 cm), ultrasound-guided FNA directed at several areas within the nodule may reduce the risk of a false negative biopsy.
Where available, we suggest using an mRNA classifier system (gene expresser classifier), mutational analysis (using a broad next-generation sequencing assay with an expanded panel of point mutations and gene fusions), or combined testing for further evaluating FNA aspirates with indeterminate cytology (follicular lesion/atypia of undetermined significance [FLUS/AUS]) or follicular neoplasm.]
- What percent of individuals have a pyramidal lobe of the thyroid?
- What is a lingual thyroid?
- What is the risk of malignancy in lingual thyroid?
- What percent of individuals have a pyramidal lobe of the thyroid? 10%
- What is a lingual thyroid? Thyroid tissue that persists in the foramen cecum at the base of the tongue (Only thyroid tissue in 70% of patients who have it)
- What is the risk of malignancy in lingual thyroid? 2%
[Treatment for lingual thyroid thyroxine suppression and 131I ablation. Resect if worried about cancer or if it does not shrink after medical therapy.]
Which 3 arteries supply the thyroid gland and from where do they originate?
- Superior thyroid artery: 1st branch of the external carotid artery
- Inferior thyroid artery: Branch of the thyrocervical trunk
- Ima artery: Originates from the innominate artery or the aorta
[The ima goes to the isthmus and is only present in 1% of cases.]
What is the name of the posterior medial suspensory ligament of the thyroid that should be dissected carefully during thyroid surgery due to proximity to the recurrent laryngeal nerve?
Ligament of Berry
