Surgical Recall - Ch. 58 Thyroid Gland Flashcards
Define the arterial blood supply to the thyroid.
Two arteries:
- Superior thyroid artery (first branch of the external carotid artery)
- Inferior thyroid artery (branch of thyrocervical trunk) (IMA artery rare)
What is the venous drainage of the thyroid
Three veins:
- Superior thyroid vein
- Middle thyroid vein
- Inferior thyroid vein
Which paired nerves must be carefully identified during a thyroidectomy?
What other nerve is at risk during a thyroidectomy and what are the symptoms?
Recurrent laryngeal nerves, which are found in the tracheoesophageal grooves and dive behind the cricothyroid muscle; damage to these nerves paralyzes laryngeal abductors and causes hoarseness if unilateral, and airway obstruction if bilateral
Superior laryngeal nerves; if damaged, patient will have a deeper and quieter voice (unable to hit high pitches)
What is the most common site of conversion of T4 to T3?
Peripheral (e.g., liver)
What is Synthroid (levothyroxine): T3 or T4?
What is the half-life of Synthroid?
T4
Half-life: 7 days
What do parafollicular cells secrete?
Calcitonin
What is the differential diagnosis of a thyroid nodule?
- Multinodular goiter
- Adenoma
- Hyperfunctioning adenoma
- Cyst
- Thyroiditis
- Carcinoma/lymphoma
- Parathyroid carcinoma
Name three types of nonthyroidal neck masses.
- Inflammatory lesions (e.g., abscess, lymphadenitis)
- Congenital lesions (i.e., thyroglossal duct [midline], branchial cleft cyst [lateral])
-
Malignant lesions:
- Lymphoma
- Metastases
- SCC
Thyroid Nodule
- What studies can be used to evaluate a thyroid nodule?
- What is the diagnostic test of choice for thyroid nodule?
- Hot vs. cold nodule?
- What are the indications for a 123I scintiscan?
- What is the most common cause of thyroid enlargement?
- What is Plummer’s disease?
Thyroid Nodule
- Studies:
- U/S–solid or cystic nodule
- FNA –> cytology
- 123I scintiscan–hot or cold nodule
- Dx test of choice for thyroid nodule? FNA
- Nodule uptake of IV 131I or 90mT
- Hot = Increased 123I uptake = functioning/hyperfunctioning nodule
- Cold = Decreased 123I uptake = nonfunctioning nodule
- Indications:
- Nodule with multiple “nondiagnostic” FNAs with low TSH
- Nodule with thyrotoxicosis and low TSH
- Multinodular goiter
- Toxic multinodular goiter
Thyroid Carcinoma
- Name the FIVE main types of thyroid carcinoma and their relative %
- What are the signs/sx?
- What comprises the workup?
- What oncogenes are associated with thyroid cancers?
Thyroid Carcinoma
- Name the FIVE main types of thyroid carcinoma and their relative %
- Papillary carcinoma: 80%
- Follicular: 10%
- Medullary: 5%
- Hurthle cell: 4%
- Anaplastic/undifferentiated: 1%
- Mass/nodule, lymphadenopathy; most are euthyroid
- FNA, thyroid U/S, TSH, calcium level, CXR, +/- scintiscan 123I
- Ras gene family and RET protooncogene
Papillary Adenocarcinoma
- What is the environmental risk?
- What are the associated histological findings?
- Describe the route and rate of spread.
- 131I uptake?
- What is the 10 year survival rate?
- What is the treatment for: <1.5 cm and no hx of neck radiation exposure?
- What postop medication should be administered?
- What is the most common site of distant mets?
Papillary Adenocarcinoma
- What is the environmental risk? Radiation exposure
- What are the associated histological findings? Psammoma bodies (round, laminar collections of calcified tissue)
- Describe the route and rate of spread. Most spread via lymphatics (cervical adenopathy); spread occurs slowly
- 131I uptake? Good uptake… so perform postop 131I scan to dx/treat metastases
- What is the 10 year survival rate? 95%
- What is the treatment for: <1.5 cm and no hx of neck radiation exposure? Thyroid lobectomy and isthmectomy / Total thyroidectomy
- What postop medication should be administered? TH replacement, to suppress TSH
- What is the most common site of distant mets? Pulmonary (lungs)
Follicular adenocarcinoma
- Describe the nodule consistency.
- What is the route of spread?
- 131I uptake?
- What is the overall 10-year survival rate?
- Can the diagnosis be made by FNA?
- What histologic findings define malignancy in follicular cancer?
- What is the most common site of distant metastasis?
- What is the treatment for follicular cancer?
Follicular adenocarcinoma
- Describe the nodule consistency. Rubber, encapsulated.
- What is the route of spread? Hematogenous, more aggressive than papillary adenocarcinoma
- 131I uptake? Good uptake…
- What is the overall 10-year survival rate? 85%
- Can the dx be made by FNA? NO; tissue structure needed for dx
- What histologic findings define malignancy in follicular cancer? Capsular or blood vessel invasion
- What is the most common site of distant metastasis? Bone
- What is the treatment for follicular cancer? Total thyroidectomy
Hurthle Cell Thyroid Cancer
- What is the cell of origin?
- 131I uptake?
- How is the dx made?
- What is the route of metastasis?
- What is the tx?
- What is the 10-year survival rate?
Hurthle Cell Thyroid Cancer
- What is the cell of origin? Follicular cells
- 131I uptake? No uptake
- How is the dx made? FNA can identify cells, but malignancy can be determined only by tissue histology (like follicular cancer)
- What is the route of metastasis? Lymphatic > hematogenous
- What is the tx? Total thyroidectomy –> RADIOIODINE ABLATION
- What is the 10-year survival rate? 80%
Medullary Carcinoma
- With what other conditions is it associated?
- Histology?
- What does it secrete?
- What is the appropriate stimulation test?
- Describe the route of spread.
- How is the dx made?
- 131I uptake?
- What is the associated genetic mutation?
- What is the 10-year survival rate?
- What should all pts with medullary thyroid cancer also be screened for?
- What is the tx?
Medullary Carcinoma
- With what other conditions is it associated? MEN type II; AD genetic transmission
- Histology? Amyloid
- What does it secrete? Calcitonin (tumor marker) –> can cause diarrhea and flushing symptoms
- What is the appropriate stimulation test? Pentagastrin (causes an increase in calcitonin
- Describe the route of spread. Lymphatic and hematogenous distant metastasis
- How is the dx made? FNA
- 131I uptake? Poor uptake
- What is the associated genetic mutation? RET proto-oncogene
- What is the 10-year survival rate? 80% w/o LN involvement, 45% with LN spread
- What should all pts with medullary thyroid cancer also be screened for? MEN II: pheo, HPTH
- What is the tx? Total thyroidectomy and median lymph node dissection… modified neck dissection, if lateral cervical nodes are positive
Anaplastic Carcinoma
- What is it?
- What is the gender preference?
- What are the associated histologic findings?
- 131I uptake?
- How is the dx made?
- What is the major differential dx?
- What is the tx of the following disorders:
- Small tumors?
- Airway compromise?
- What is the prognosis?
Anaplastic Carcinoma
- What is it? Undifferentiated cancer arising in ~75% of previously differentiated thyroid cancers (most commonly, follicular)
- What is the gender preference? Women > Men
- What are the associated histologic findings? Giant cells, spindle cells
- 131I uptake? Very poor uptake
- How is the dx made? FNA (large tumor)
- What is the major differential dx? Thyroid lymphoma (much better prognosis!)
- What is the tx of the following disorders:
- Small tumors? Total thyroidectomy + XRT/chemo
- Airway compromise? Debulking surgery + tracheostomy, XRT/chemo
- What is the prognosis? Dismal, b/c most pts are at stage IV at presentation (3% alive in 5 years)