Thyroid Cancer Types Clinical Overview
I. The "On-Call" Snapshot
Clinical Significance in Malaysia: This is the most common endocrine malignancy you will encounter. Papillary carcinoma accounts for about 80% of all thyroid cancers in Malaysia, so you are guaranteed to see it.
High-Yield Definition: Differentiated thyroid carcinomas (DTCs) are malignancies arising from thyroid follicular epithelial cells that retain characteristics of normal thyroid tissue, such as the ability to produce thyroglobulin (Tg) and take up iodine.
Clinical One-Liner: These are the "good" thyroid cancers—slow-growing, highly treatable, and usually with an excellent prognosis if caught early.
II. Etiology & Risk Factors
Etiology: Arises from thyroid follicular cells. The exact cause is multifactorial, involving genetic mutations (e.g., BRAF V600E in papillary, RAS or PAX8/PPARγ rearrangement in follicular) and environmental triggers.
Risk Factors:
Non-Modifiable:
Female gender (3:1 ratio to males)
Age (peaks at 30-50 years)
Family history of thyroid cancer
Certain genetic syndromes (e.g., Familial Adenomatous Polyposis)
Modifiable/Environmental:
History of radiation exposure to the head and neck, especially in childhood. This is a major one.
Iodine deficiency (stronger link for Follicular Ca)
III. Quick Pathophysiology
Follicular cells undergo malignant transformation but still resemble normal cells. Papillary carcinoma characteristically spreads via lymphatics to cervical lymph nodes. Follicular carcinoma is different; it prefers to invade blood vessels (hematogenous spread) and can metastasize to distant sites like the lungs and bones, often before any lymph node involvement. This is why we treat them slightly differently.
IV. Clinical Assessment
Red Flags & Immediate Actions:
Rapidly enlarging neck mass: Needs urgent ultrasound and specialist review.
Hoarseness (Dysphonia): Suggests recurrent laryngeal nerve involvement. Scope the patient and inform your senior.
Hard, fixed neck lump: Concerning for local invasion.
Cervical lymphadenopathy: Palpable nodes suggest lymphatic spread.
History:
Common (>50%): Usually asymptomatic, presents as a palpable, painless thyroid nodule found incidentally or by the patient.
Less Common (10-50%): Compressive symptoms like dysphagia (difficulty swallowing) or a choking sensation if the nodule is large.
Pertinent Negatives: Ask about a lack of thyroid dysfunction symptoms (most are euthyroid), no pain, and no history of recent fever or neck tenderness (points away from thyroiditis).
Physical Examination:
Inspection: Look for a visible mass in the anterior neck that moves with swallowing.
Palpation: Assess the thyroid nodule for size, consistency (firm vs. hard), and fixation to surrounding tissues. Meticulously examine cervical lymph node chains (central, lateral).
Clinical Pearl: The vast majority of thyroid nodules are benign. Our job is to pick out the suspicious ones. A solitary, firm nodule in a very young (<30) or older (>60) patient is more worrying than a multinodular goitre in a middle-aged female.
V. Diagnostic Workflow
Differential Diagnosis:
Benign Colloid Nodule/Multinodular Goitre:
Points For: Very common, often multiple nodules, soft consistency.
Points Against: Rapid growth, hard consistency, lymph nodes.
How to Differentiate: Ultrasound features and Fine Needle Aspiration Cytology (FNAC).
Thyroid Cyst:
Points For: Smooth, soft, may fluctuate in size.
Points Against: Solid components on ultrasound.
How to Differentiate: Ultrasound will show anechoic (black) fluid-filled cavity.
Thyroiditis (e.g., Hashimoto's):
Points For: Often associated with hypothyroidism, diffuse goitre.
Points Against: A discrete, hard nodule.
How to Differentiate: Thyroid function tests and auto-antibodies (Anti-TPO, Anti-Tg).
Investigations Plan:
Bedside / Initial:
Thyroid Function Test (TSH): To assess functional status. Most patients are euthyroid. A suppressed TSH suggests a "hot" (hyperfunctioning) nodule, which is rarely malignant.
First-Line Imaging:
Ultrasound of the Neck: This is the most crucial initial imaging. We look for suspicious features: microcalcifications, hypoechogenicity, irregular margins, taller-than-wide shape, and central vascularity. The ultrasound report will give a TIRADS score to stratify risk.
Confirmatory / Gold Standard:
Ultrasound-guided Fine Needle Aspiration Cytology (FNAC): This is the diagnostic procedure of choice for suspicious nodules. The pathologist will report it using the Bethesda System for Reporting Thyroid Cytopathology.
Note: FNAC can diagnose Papillary carcinoma well. For Follicular lesions, it's tricky. Cytology can only suggest a "Follicular Neoplasm" (Bethesda IV). The definitive diagnosis of Follicular carcinoma requires surgical excision to look for capsular or vascular invasion on histology.
VI. Management Plan (Simplified)
Based on FNAC and staging:
Surgery: This is the primary treatment. The extent depends on tumour size, spread, and patient factors.
Total Thyroidectomy: The standard procedure for most DTCs >1 cm.
Lobectomy: May be an option for small (<1 cm), low-risk, unifocal, intrathyroidal papillary microcarcinomas.
Neck Dissection: Performed if there is evidence of lymph node metastasis.
Post-Operative Radioactive Iodine (RAI) Ablation:
Used after total thyroidectomy for patients with higher-risk disease (large tumours, lymph node spread, distant mets) to destroy any remaining thyroid tissue (remnant ablation) and treat microscopic disease.
TSH Suppression Therapy:
After surgery, patients are started on lifelong levothyroxine. We aim for a TSH level that is suppressed (low) to prevent any remaining cancer cells from being stimulated to grow by TSH. The degree of suppression depends on the patient's risk of recurrence.
VII. Prognosis
Excellent. The 10-year survival rate for localized papillary carcinoma is >95%. Follicular carcinoma is slightly lower but still very good if confined to the thyroid.
Prognostic Factors: Age at diagnosis (worse for >55), tumour size, presence of distant metastases, and extent of local invasion.
VIII. How to Present to Your Senior
"Dr, for your review. This is Puan Siti in Clinic Room 2, a 45-year-old lady who presented with a self-palpated painless neck lump. She is clinically and biochemically euthyroid. Ultrasound showed a 2cm solid, hypoechoic nodule in the right thyroid lobe with microcalcifications, TIRADS 5. The FNAC came back as Bethesda VI: Papillary Thyroid Carcinoma. I am referring her to the endocrine surgery team for consideration of total thyroidectomy."
IX. Summary & Further Reading
Top 3 Takeaways:
DTCs are the most common thyroid cancers with an excellent prognosis.
Ultrasound is the key initial investigation, and FNAC provides the diagnosis.
Management is primarily surgical (Total Thyroidectomy), often followed by RAI and TSH suppression.
Key Resources:
UpToDate: "Differentiated thyroid cancer: Overview of management"
American Thyroid Association (ATA) Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer. (These are the international standard).
