Thyroid Cancer Associated with Hashimoto Thyroiditis
The most common type of thyroid cancer associated with Hashimoto thyroiditis is Papillary Thyroid Cancer (PTC). 1, 2
Evidence for Papillary Thyroid Cancer Association
The association between Hashimoto thyroiditis and papillary thyroid cancer is well-documented in the medical literature:
- Papillary thyroid cancer is the most frequently encountered malignancy in patients with Hashimoto thyroiditis 2
- The lymphocytic infiltration characteristic of Hashimoto thyroiditis is frequently found in thyroid glands resected for papillary carcinoma 2
- In a 2022 study, the frequency of Hashimoto thyroiditis in papillary thyroid cancer patients was found to be 34.27% 3
Clinical Characteristics of PTC with Hashimoto Thyroiditis
Patients with papillary thyroid cancer and coexistent Hashimoto thyroiditis typically present with:
- Less aggressive disease characteristics 1
- Superior 10-year disease-specific survival 1
- Better recurrence-free survival 1
- Decreased PTC-related mortality (HR, 0.19) 1
- Higher cure rates (75.3% vs 47.1% in PTC without Hashimoto thyroiditis) 3
- Less persistent disease (6.8% vs 22.9% in PTC without Hashimoto thyroiditis) 3
Regional Variations and Exceptions
It's important to note that in certain populations, particularly those in endemic goiter areas, PTC with Hashimoto thyroiditis may display more aggressive features:
- More frequent lymph node invasion 1, 4
- Increased extra-thyroidal extension 1, 4
- Higher incidence of aggressive histological PTC variants 1, 4
Other Thyroid Cancers Associated with Hashimoto Thyroiditis
While papillary thyroid cancer is the most common, other associations exist:
- Thyroid Lymphoma: Has a strong association with Hashimoto thyroiditis, with a reported relative risk of 9.74 (95% CI 3.93-24.13) 1
- The relationship between thyroid lymphoma and Hashimoto thyroiditis appears to be well established 2
- Follicular Carcinoma: Much less commonly associated with Hashimoto thyroiditis 5
Diagnostic Considerations
For patients with Hashimoto thyroiditis:
- Fine-needle aspiration (FNA) is recommended for suspicious thyroid nodules 1
- Be aware that PTC with Hashimoto thyroiditis may display prominent stromal desmoplasia and pseudovascular patterns, which can present diagnostic challenges 5
- On ultrasound, hypoechoic nodules accompanied by multiple echogenic spots may indicate PTC in patients with Hashimoto thyroiditis 6
- Close follow-up and meticulous sonographic examinations are warranted in patients with Hashimoto thyroiditis due to the potential for papillary carcinoma development 6