Thyroid – Flashcard
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Name the 4 anatomic subdivisions / lobes of the thyroid
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Right Lobe Left Lobe Isthmus Pyramidal Lobe
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What is the fx of the epithelial cells in the thyroid follicle?
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Remove iodide from blood Forms T3, T4 thyroid hormones
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What is the fx of the parafollicular cells in the thyroid follicle?
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Produce calcitonin * Aka C cells
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What are the 3 main histologies of thyroid cancer?
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Follicular-epithelial (94%) Medullary (2-4%) Anaplastic (2%)
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What are 3 subtypes of follicular-epithelial?
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Papillary (most common) Follicular Hurthle cell
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What is the incidence of papillary thyroid cancer in autopsy series?
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30-40% have microcarcinomas
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What is typical age at dx for follicular vs. papillary thyroid cancer?
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Follicular: 40-60 yrs Papillary: 30-50 yrs
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What is gender ratio for papillary and follicular thyroid cancers?
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female : male (3:1)
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What is strongest predictor for papillary thyroid cancer?
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RT exposure as child No increased risk of exposure after 20
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Name 4 genetic disorders associated with papillary thyroid cancer.
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FAP Gardner's syn Turcot syn Familial papillary carcinoma
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Name genetic disorder associated with follicular thyroid cancer
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Cowden syn
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Medullary thyroid cancer arises from what cell?
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Parafollicular C cells (produce calcitonin)
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Name 2 genetic disorders associated with medullary thyroid cancer
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MEN 2a MEN 2b
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What % medullary cancers are related to genetic syndrome?
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25%
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What nerve lies in tracheoesophageal groove, post to right/left thyroid lobes?
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Recurrent laryngeal
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What are primary, secondary, and tertiary lymphatic drainage of thyroid?
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Primary: Level VI TE groove delphian LN Secondary: cervical / SCV LN Tertiary: sup mediastinal / RP LN
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What % of palpable thyroid nodules are malignant?
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5%
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In pt with low TSH and nodule that shows uptake by I-123 or Tc-99 what is likely dx?
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Adenoma
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Which follicular-epithelial derived thyroid subtypes are difficult to distinguish from adenomas on FNA?
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Follicular Hurthle cell Only show follicular structures Papillary shows both papillary & follicular strs that help to distinguish from adenoma
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What pathologic criteria must be met to make dx of Hurthle cell cancer?
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Hypercellularity w/ > 75% Hurthle cells (aka oncocytic cells) Hurthle cells characterized by abundant eosinophilic granular content
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Which thyroid cancer subtype is more likely to present with N+ dz: papillary or follicular?
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Papillary (30%) Follicular (10%)
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Name the 2 major & 3 minor prognostic factors for follicular-epithelial derived thyroid cancer.
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Major: age, tumor size Minor: histo, local ext, LN status
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For follicular-epithelial derived cancers what is T staging?
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T1: < 2cm (1a: 2cm) T2: 2-4 cm (limited to thyroid) T3: > 4cm (min extrathyroid ext) T4a: local ext but resectable T4b: unresectable
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What is difference b/w N1a and N1b in thyroid cancer?
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N1a: pre/para-trach, pre-laryngeal (VI) LN N1b: levels I-V, upper mediastinum
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What are stage groupings for pts < 45 with thyroid cancer?
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I: M0 II: M1
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What are stage groupings for pts > 45 with thyroid cancer?
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I: T1N0 II: T2N0 III: T3N0, T1-3N1a IVA: T4a, N1b IVb: T4b IVc: M1
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What is the delphian LN?
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Pre-laryngeal LN
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What must be done prior to I-123 or I-131 scan?
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TSH stimulation
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What are 2 methods to do TSH stimulation?
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Thyroid hormone withdrawal Recombinant TSH
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What are some advantages of TSH stimulation?
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Fewer side effects and shorter period of elevated TSH (theoretical lower risk of tumor progression)
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What are approved indications for rTSH?
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Follow-up iodide scans I-131 tx of low risk pts
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What % of follicular-epithelial derived cancers will have residual uptake on iodide scan after thyroidectomy?
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80%
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What other body sites will show increased iodide uptake?
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Salivary glands GI tract * Both have iodide transporters
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Which type of thyroid cancer has the best prognosis?
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Papillary OS10: 93% (vs. 85% for follicular)
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To what thyroid cancer subtype is the presentation of Hurthle cell cancer the most similar?
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Follicular * Hurthle cell cancers have higher DM rate & worse prognosis (OS10 ~76%)
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What is OS10 for pts with localized vs. N+ medullary thyroid cancer?
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Localized: 90% N+: 70%
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What are stage grouping for anaplastic?
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IVA: resectable IVB: unresectable IVC: mets
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What is MS and OS1 for pts with anaplastic histo?
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MS 6 mos OS1 ~20%
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Does tall cell variant have a more favorable or less favorable prognosis when compared to classic papillary thyroid cancer?
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Unfavorable
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What is tx paradigm for follicular-epithelial derived thyroid cancer?
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Surg (even if M1) -> obs vs. adj tx
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What are 3 surgical options for thyroid cancer?
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Lobectomy + isthmusectomy Near-total thyroidectomy Total thyroidectomy
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What is difference b/w near-total and total thyroidectomy?
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Near-total is less aggressive around recurrent laryngeal n.
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For which pts with papillary thyroid cancer is lobectomy + isthmusectomy adequate?
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Controversial Good option for pts with none of following risk factors: > 45 tumor > 4 aggressive histo prior hx of RT DM LN+ local ext +margins
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What is one reason to do total thyroidectomy?
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easier f/u with whole-body iodide scans Also improves LC
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What are 4 indications for adjuvant tx after GTR in follicular-epithelial derived thyroid cancer?
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1. >4 cm tumor 2. LN+ or DM 3. Aggressive histo 4. pT4 + papillary histo & age < 45
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What 5 aggressive histo subtypes merit consideration of adj tx?
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Tall cell Columnar cell Insular cell Oxyphilic Poorly differentiated
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What is adj tx paradigm for follicular-epithelial derived thyroid cancer?
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Long-term TSH suppression alone or with I-131 +/- EBRT
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What are indications for adj I-131 in addition to TSH suppression for thyroid cancer?
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Suspected or proven residual thyroid tissue or residual tumor
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What is mCi dose range to ablate residual normal thyroid tissue?
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30-100 mCi
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What is mCi dose range to ablate residual thyroid cancer?
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100-200 mCi
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What are 4 indications for adj EBRT in addition to TSH suppression and I-131 for thyroid cancer?
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1. pT4 papillary & > 45 yrs 2. Gross dz after I-131 3. Bulky mets after I-131 4. Lesions with inadequate iodide uptake
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What 3 regions should be irradiated w/ EBRT in pt < 45 with pT4 papillary thyroid cancer?
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Thyroid bed Bilat necks Upper mediastinal LN
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What are EBRT doses for thyroid cancer?
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Gross dz: 68-70 in 2 Gy fx Micro dz: 60 Gy Low risk LN: 45-50 Gy
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What is the tx paradigm for medullary thyroid cancer?
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Definitive surgery EBRT for palliation
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What is tx paradigm for anaplastic subtype?
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Max safe resection -> chemoRT Some promising results with post-op cis/dox before & after 40 Gy BID
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For what group of anaplastic pts does PORT improve outcome?
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T4b (extra-thyroid ext) but NOT T4b (thyroid confined) Stage IVc (mets)
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What is prognosis for pts with locoregional vs. distant recurrence of follicular-epithelial derived thyroid cancer?
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Excellent if local (OS 80-90%) Worse with distant
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What are acute side effects of > 100 mCi I-131?
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GI irritation Sialadenitis Cystitis
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What are 3 most important long-term side effects of > 100 mCi of I-131?
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Pulmonary fibrosis Oligospermia Leukemia
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What does follow-up of thyroid cancer pts entail?
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H&P + TSH / thyroglobulin levels at 6, 12 mos then annually if no dz Neck US TSH-stimulated iodine scans
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What other imaging can be considered if I-131 scan is negative but stimulated thryoglobulin level is elevated?
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PET/CT
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What is max lifetime dose of I-131?
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800-1000 mCi
