Endocrine Surgery JC039: A Thyroid Nodule: Benign Thyroid Nodules, Thyroid Cancer Flashcards

Question

WDTC: De-escalation of treatment / De-intensifying care

Answer 1

Principle: - Avoid overtreatment - Treat patients appropriately Evolving towards: 1. **Active surveillance** 2. **Less than total thyroidectomy** (∵ not much difference in cumulative death risk compared to hemithyroidectomy) 3. **Avoid routine neck dissection** —> avoid complications e.g. hypoparathyroidism 4. Less adjuvant I131 therapy (not all patients require esp. if only hemithyroidectomy) 5. Avoid screening + overdiagnosis (∵ very low mortality / clinically insignificant anyway) —> ↑ treatment (waste resource) —> thyroid USG not routinely recommended for healthy subjects

Answer 2

**Neuroendocrine tumour** - Arise from **Parafollicular C cells** - 25-50% familial Marker: - **Calcitonin** (basal / stimulated) Management: - Total thyroidectomy - Central +/- Lateral neck dissection Familial cases (1/3): - **MEN2A** - **MEN2B** - Familial MTC Diagnosis: - Genetic analysis: **RET proto-oncogene** (~100% penetrance) —> may perform Prophylactic thyroidectomy (at 5-10 yo) at stage of **C cell hyperplasia** before develop into clinically invasive cancer Prognosis: - Worse than WDTC

Answer 3

- One of most aggressive cancer in human - Uncommon (possibly ∵ early treatment of well-differentiated thyroid cancer) - Elderly with poor co-morbid state - Aggressive + rapidly growing - Locally advanced disease at clinical presentation - Frequent distant metastasis - Lack of effective treatment: **Chemoirradiation +/- Resection +/- Targeted therapy (palliative only)** - Invariable palliative + fatal (**4-6 months survival**)

Answer 4

Hyperthyroidism: 1. **Anti-thyroid medications** until **Euthyroid** - avoid precipitation of **thyroid storm during operation** 2. **β-blockers** for 2 weeks (3. Old practice: **Lugol’s iodine** 5 days before operation (may **reduce blood loss during operation**)) Myxoedema coma: - Give IV Hydrocortisone with IV Thyroxine otherwise Cortisol metabolised by ↑ Thyroxine Papillary Thyroid carcinoma: 1. Post-op I131 - **Thyroxine withdrawal** (for 4 weeks beforehand) vs **Thyrogen** (**Synthetic TSH** 1-2 days beforehand) —> allow ↑ TSH production from pituitary —> **↑ Iodine uptake by residual thyroid tissue / tumour cells** 2. **T4 suppressive therapy** —> suppress TSH to ↓ tumour recurrence

Answer 5

3 bony structures: 1. Hyoid bone 2. Thyroid cartilage 3. Cricoid cartilage - complete ring - mark upper limit of isthmus - divide thyroid horizontally into upper 1/3 (i.e. upper pole) + lower 2/3 (i.e. middle + lower pole) Thyroid gland: 1. Left / Right lobe (cover 2/3 of trachea) 2. Isthmus (cover 2nd + 3rd tracheal ring) 3. Pyramidal lobe Recurrent laryngeal nerve: - Run along **tracheo-esophageal groove** —> Readily infiltrated by tumour located at back of Thyroid lobe —> hoarseness - Need to be identified during surgery Central compartment: - SC fat around thyroid - Level 6 LN (pretracheal + paratracheal) Lateral compartment: - Level 2-5 LN

Answer 6

Surgery: 1. Primary tumour - Hemi / Total Thyroidectomy —> choice depends on **Size + Tumour prognostic features** —> **<4cm diameter + no poor prognostic features** —> Hemithyroidectomy (ATA guideline: - **>1cm, <4cm** AND - **without extrathyroid extension** AND - **without clinical evidence of LN metastasis** —> Bilateral (near-total / total) or Unilateral (hemi) are acceptable —> Hemi: may be sufficient initial treatment for **low risk papillary / follicular carcinoma** —> Total: enable **RAI therapy** / enhance **follow-up based upon disease features / patient preference**) 2. Metastatic cervical LN - **Central compartment neck dissection** (often performed at time of surgery, for all patients regardless of whether there are enlarged central LN —> **prophylactic**) - **Lateral compartment Functional neck dissection** (level 2-5) (only done when proven disease in the compartment) - **Lateral compartment Selective neck dissection** (level 2-5) (only done when proven disease in the compartment) - Compartmental neck dissection - Excision of LN - “Prophylactic” neck dissection (Level 1 LN never involved) Adjuvant therapy (required for Intermediate / High risk tumours): 1. **Radioactive iodine** - 30-100mCi - given **2 months after surgery** - given **T4 withdrawal / recombinant TSH injection** (from ERS15: ↑ Iodine uptake by residual thyroid tissue / tumour cells) - dosage decreasing recently ∵ efficacy shown similar between low / high dose - post-therapy scan 5-8 days after - whole body scan 6-12 months after - therapy to distant metastases: 100-200mCi 2. **T4 suppressive therapy** - lower TSH level <0.03 3. **External beam RT** - reserved for patients unable to undergo complete excision i.e. **residual gross tumour tissue** 4. Chemotherapy (**NOT given since most tumours are chemo-resistant**) - doxorubicin as a radiation sensitiser

Answer 7

Removal of lymphatics in the neck that harbours cancer metastasis **Radical neck dissection**: Removal of - Level 1-5 LN (ipsilateral) - SCM - IJV - CN11 (pass through lymphatic layer) - Cervical plexus (pass through lymphatic layer) (functional deficit but acceptable) **Modified radical neck dissection**: Modification of radical neck dissection by preserving: - SCM - IJV - CN11 —> Aim: improving functional outcome without jeopardising control of nodal disease **Selective neck dissection**: Removal of certain areas of LN that has highest chance of occult nodal metastasis - Oral tongue cancer —> Supraomohyoid neck dissection (Level 1-3) for oral tongue cancer - Tonsil cancer —> Level 2-4 - Thyroid cancer —> Central compartment dissection (bilateral level 6) —> usually reserved for patients with no clinical evidence of nodal metastasis but cancer has high chance of occult nodal metastasis

Answer 8

**2015 ATA risk stratification system**: - Low / Intermediate / High risk - Predict likelihood of WDTC recurring after complete excision - Number + Size of involved LN carry prognostic significance - Genetic mutation e.g. BRAFV600E —> higher recurrence risk AJCC TNM staging (8th edition): - Age **>=55 an important parameter**

Answer 9

High risk: - Age >55 - Tumour size >2cm - Extrathyroidal extension - Incomplete resection of primary tumour (R2) - Distant metastasis Management: 1. **Total / Near-total thyroidectomy** 2. **Central compartment neck dissection** (+/- Compartmental neck dissection) 3. **Radioactive iodine ablation** 4. **Thyroxine suppressive therapy** (keep TSH <0.03) 5. **External beam RT** (**for incomplete resection R2**) (Prognostic risk classification for WDTC: (from SpC Bedside) **AGES / AMES**: High risk: - Age >40 - Male - Grade / Metastasis: Poorly differentiated / Metastasis - Extent: Capsular invasion, Extrathyroidal extension - Size: >4cm)

Answer 10

Life-long (Interval 3 months - 1 year) 1. Clinical examination (H+N region) 2. **Thyroid function test** 3. **Thyroglobulin** (from SpC Bedside: take **Anti-Thyroglobulin Ab** as well) 4. CXR 5. USG (+/- FNAC) 6. **WBS** (whole body scan) 7. PET (if WBS negative)

Answer 11

Occult: - Clinical not obvious but discovered post-mortem by pathologist (very common: 1 in 5) Minimal (Micro): - <=1cm diameter - Associated with excellent prognosis - Not all occult carcinoma are microcarcinoma

Answer 12

- Behave very differently from PTC - Present with **distant metastases via blood** Metastasis: 1. LN metastases 10-15% 2. **Haematogenous spread** - Lungs - Bone If FNAC show follicular cytology —> can be **adenoma / carcinoma** Treatment: 1. **Hemithyroidectomy** (∵ not possible to differentiate follicular adenoma vs carcinoma by FNAC alone) —> Wait for **Paraffin section** (5-7 days later) —> Widely-invasive / Angio-invasive FTC —> Completion total thyroidectomy —> Minimally invasive (encapsulated) FTC —> Observation sufficient - **Paraffin section** (Frozen section not routinely performed) —> diagnostic information in 13% —> surgical procedure modified in 3.3% —> misguided intervention in 5% Management of FTC with distant metastasis: 1. Histological confirmation of metastasis 2. +/- Detection of primary tumour 3. Total thyroidectomy 4. Adjuvant therapy - Ablation - Radioactive iodine - Thyroxine suppression therapy

Answer 13

1. Vocal cord dysfunction (unilateral / bilateral) - **RLN (Infraglottic) / External branch of Superior laryngeal nerve** (Supraglottic: Cricothyroid) - transient / permanent 2. **Hypoparathyroidism** (∵ injury / removal of parathyroid gland) - transient / permanent 3. Bleeding - superficial / deep 4. **Tracheomalacia** (cartilage in trachea collapses especially during increased airflow) 5. Wound complications - Seroma - Hypertrophic scar 6. **Thyroid storm** 7. Others **Post-op Monitoring**: 1. Voice 2. **Ca level** (6-12 hours after operation) (Hypoparathyroidism) 3. SOB, Compression sensation 4. **HR, temperature** (Thyroid storm) 5. Infection 6. Keloid scar

Answer 14

Autosomal dominant (AD) Clinical features: 1. Primary hyperparathyroidism - most common feature - asymmetric multiglandular involvement - current view: multiple adenomas rather than hyperplasia 2. Pancreatic neuroendocrine tumours - most are functional —> Gastrinoma (50%) —> Insulinoma (20%) —> Glucagonoma (3%) —> VIPoma (1%) 3. Pituitary adenomas 4. Others (Lipomas, Adrenal adenomas, Thymic carcinoids etc.) - 50% probability of death by 50 yo

Answer 15

- 75% of MEN type 2 - Caused by germline mutation of **RET gene** Clinical features: 1. Medullary thyroid carcinoma (>90%) - can be treated during pre-symptomatic stage due to early detection of germline RET gene mutation 2. Phaeochromocytoma (50%) 3. Hyperparathyroidism (20-30%) Prognosis: - Better than MEN1