What Are Thyroid Malignancies?
Thyroid malignancies refer to cancers originating in the thyroid gland. These tumors may be well-differentiated (papillary and follicular), moderately differentiated (medullary), or undifferentiated (anaplastic). Each subtype presents unique diagnostic and therapeutic challenges, with varying survival outcomes.
Thyroid Cancer Types and Histology
| Type | % of Cases | Cell of Origin | Differentiation | Spread |
|---|---|---|---|---|
| Papillary | 60% | Epithelial | Well | Lymphatic |
| Follicular | 25% | Epithelial | Well | Hematogenous |
| Anaplastic | 10% | Epithelial | Poor | Direct, lymphatic, hematogenous |
| Medullary | 5% | Parafollicular (C cells) | Moderate | Lymphatic and hematogenous |
Epidemiology and Risk Factors
- Male:Female ratio is approximately 1:2
- Papillary: Most common in young adults
- Follicular: Typically occurs in middle-aged individuals
- Anaplastic: Affects the elderly
- Medullary: Can present at any age; associated with MEN II syndromes
Risk Factors:
- History of radiation exposure to the neck
- Family history of thyroid cancer
- Pre-existing goitre
- Genetic syndromes like MEN IIA & IIB
Clinical Presentation by Type
Papillary Carcinoma
- Commonly presents as a solitary thyroid nodule
- Frequently metastasizes to cervical lymph nodes
- Often indolent with excellent prognosis
Follicular Carcinoma
- Tends to spread hematogenously to lungs and bones
- Symptoms from distant metastases like pain or swelling
Anaplastic Carcinoma
- Rapidly enlarging neck mass
- Can cause tracheal or esophageal compression
- Presents with stridor, cough, dysphagia
Medullary Carcinoma
- May be sporadic or familial (MEN IIA/IIB)
- Associated with calcitonin secretion
- May cause diarrhea, flushing
How Thyroid Cancer Spreads
| Route | Sites Affected |
|---|---|
| Local | Trachea, Esophagus, Pharynx |
| Lymphatic | Jugular, Supraclavicular nodes |
| Hematogenous | Brain, Lungs, Liver, Bone, Adrenals |
Voice changes (due to RLN or SLN involvement) and dysphagia are common in aggressive tumors.
Diagnostic Approach: From FNAC to Imaging
FNAC (Fine Needle Aspiration Cytology)
- First-line investigation for solitary nodules
- Distinguishes benign vs malignant lesions
Thyroid Ultrasound
- Assesses size, echogenicity, calcifications
- Detects nodal metastasis
Other Investigations
- Calcitonin levels for medullary cancer
- Serum thyroglobulin post-thyroidectomy follow-up
- Bone scan, CT, PET for distant metastasis
Treatment: Surgery, Ablation, & Therapy
Papillary & Follicular (Differentiated)
- Total thyroidectomy + lymph node dissection
- Radioactive iodine (¹³¹I) ablation
- TSH suppression therapy (levothyroxine)
Medullary Thyroid Carcinoma
- Total thyroidectomy + lymph node dissection
- Screen for pheochromocytoma before surgery
- Calcitonin monitoring post-op
- Radiotherapy/Chemo usually ineffective
Anaplastic Carcinoma
- Surgery only for palliation
- Some benefit from doxorubicin + cisplatin
- Poor prognosis—median survival <12 months
Complications of Thyroidectomy
| Phase | Complication |
|---|---|
| Intraoperative | Bleeding, pneumothorax, thyrotoxic storm |
| Early | Hypocalcemia, hematoma, RLN palsy |
| Late | Hypothyroidism, recurrence |
Voice changes may occur due to recurrent laryngeal nerve damage—laryngoscopy is essential pre-op in patients with voice changes.
Survival Rates and Prognosis
| Type | Prognosis (5-Year Survival) |
|---|---|
| Papillary | 97% (no metastasis), 50% (metastasis) |
| Follicular | 90-95% (no metastasis), 50% (metastasis) |
| Medullary | ~85% overall survival |
| Anaplastic | <12 months median survival |
FAQs on Thyroid Malignancy
Q1. Are all thyroid nodules cancerous?
No, the majority are benign, but all solitary nodules should undergo FNAC to rule out malignancy.
Q2. Can thyroid cancer affect voice?
Yes, especially if the tumor invades the recurrent laryngeal nerve (RLN) or superior laryngeal nerve (SLN).
Q3. What is the role of calcitonin?
It is a tumor marker for medullary thyroid carcinoma, used for diagnosis and post-surgical monitoring.
Q4. Is radiation therapy useful in thyroid cancer?
Only in selected cases like medullary or anaplastic variants. Most differentiated thyroid cancers respond better to radioactive iodine.
Q5. What are the “red flag” symptoms for referral?
According to 2-week wait guidelines:
- Hoarseness >6 weeks
- Neck mass >3 weeks
- Dysphagia >3 weeks
- Rapidly growing thyroid lump
- Cranial neuropathies
Conclusion
Thyroid malignancies are a diverse group of cancers, from slow-growing papillary cancers with high cure rates to aggressive anaplastic types. With timely diagnosis using FNAC and imaging, followed by appropriate surgical management, most patients can achieve excellent outcomes. Continued surveillance, especially using thyroglobulin or calcitonin, is essential for monitoring recurrence.
