Hurthle Cell Thyroid Carcinoma: Key Characteristics
Hurthle cell thyroid carcinoma is more aggressive than follicular thyroid carcinoma. 1, 2
Classification and Pathological Features
Hurthle cell carcinoma (HCC) is now recognized as a distinct entity from follicular thyroid carcinoma (FTC), rather than simply a variant. According to the 2017 WHO classification, HCC has been reclassified as a separate pathological entity 1, 3. Key pathological features include:
- Large cells with abundant eosinophilic, granular cytoplasm due to numerous mitochondria
- Hyperchromatic nucleus with prominent nucleolus
- Distinct molecular abnormalities that differentiate it from conventional follicular carcinomas 1
- "Pure" Hurthle cell carcinomas have a Hurthle-cell component exceeding 75% 1
Aggressiveness and Clinical Behavior
HCC demonstrates more aggressive behavior compared to follicular thyroid carcinoma:
- The 10-year disease-free interval is significantly lower for HCC (40.5%) compared to FTC (75%) 2
- The 10-year cause-specific mortality is higher for HCC (51%) compared to FTC (20%) 2
- HCC is more likely to present with lymph node metastases than follicular tumors 1
- HCC with extensive vascular and/or capsular invasion should be managed like other high-risk carcinomas 1
Diagnostic Challenges
HCC cannot be readily diagnosed with fine-needle aspiration:
- Preoperative diagnosis is challenging 4
- FNA cannot reliably distinguish between benign and malignant Hurthle cell lesions
- Definitive diagnosis often requires surgical excision to evaluate for capsular or vascular invasion 5
Radioactive Iodine Uptake
HCC typically does NOT show avid I-131 uptake:
- The effectiveness of radioactive iodine therapy in HCC is debated 4
- HCC is less likely to benefit from radioiodine therapy compared to follicular carcinoma 6
- This poor iodine avidity contributes to the more challenging management of metastatic disease
Risk Factors
HCC is not typically associated with previous neck radiation. Risk factors for HCC progression and poor survival include:
- Extrathyroidal invasion
- Presence of metastases at diagnosis
- Male gender
- Extent of thyroidectomy 2
Management Considerations
- Total thyroidectomy is recommended for tumors larger than 4 cm 4
- HCC with extensive vascular/capsular invasion requires aggressive management similar to other high-risk thyroid carcinomas 1
- Long-term surveillance is critical as recurrence may occur many years after initial diagnosis 3
In conclusion, Hurthle cell carcinoma represents a distinct and more aggressive form of thyroid cancer compared to follicular thyroid carcinoma, with unique molecular features, lower radioiodine avidity, and higher rates of recurrence and mortality.