Prevalence of Medullary Thyroid Cancer
Medullary thyroid cancer (MTC) is a rare malignancy that accounts for approximately 4-5% of all thyroid cancers. 1, 2
Epidemiology and Incidence
According to the National Comprehensive Cancer Network (NCCN) guidelines, MTC represents approximately 4% of all thyroid carcinomas 3
In a study of 53,856 patients treated for thyroid carcinoma between 1985 and 1995:
- 80% had papillary carcinoma
- 11% had follicular carcinoma
- 3% had Hürthle cell carcinoma
- 4% had medullary carcinoma
- 2% had anaplastic thyroid carcinoma 3
The incidence rate of MTC in the United States is approximately 0.11 per 100,000 person-years 3
Unlike other thyroid cancers, MTC shows no substantial differences in incidence by race/ethnicity or sex 3
Sporadic vs. Hereditary Forms
- Approximately 75-80% of MTC cases are sporadic in nature
- The remaining 20-25% of cases are hereditary, occurring as part of genetic syndromes 1, 4
- Hereditary forms include:
- Multiple Endocrine Neoplasia type 2A (MEN 2A)
- Multiple Endocrine Neoplasia type 2B (MEN 2B)
- Familial Medullary Thyroid Carcinoma (FMTC) 5
Prognosis and Mortality
- The 10-year disease-specific survival rate for patients with MTC is approximately 75% 3
- MTC is more aggressive than well-differentiated thyroid cancers, being responsible for 8-15% of all thyroid cancer-related deaths despite its low prevalence 6
- When diagnosed at locally advanced or metastatic stages, 10-year survival rates drop to less than 20% 6
Age and Presentation
- Sporadic MTC typically presents in the fifth or sixth decade of life
- Hereditary forms tend to present at earlier ages 5
- Approximately 50% of patients with sporadic disease present with metastatic cervical adenopathy at initial diagnosis 5
- Symptoms of upper aerodigestive tract compression or invasion occur in up to 15% of patients with sporadic disease 5
Important Clinical Considerations
- Early detection is crucial for improved outcomes, particularly in hereditary forms
- Genetic testing for RET proto-oncogene mutations is essential for family members of patients with hereditary MTC
- Surgery (total thyroidectomy with appropriate lymph node dissection) remains the primary treatment and only potential cure for MTC
- Unlike other thyroid cancers, MTC does not respond to radioactive iodine therapy and is relatively resistant to conventional chemotherapy 5
The rarity of MTC highlights the importance of proper diagnosis and management by specialists familiar with this uncommon but aggressive form of thyroid cancer.