Causes
There is often no definitive cause of medullary thyroid cancer. However, listed below are a few known risk factors for developing medullary thyroid cancer.
Genetic Factors
Medullary thyroid cancer (MTC) can be either sporadic or hereditary. Approximately 80% of cases are sporadic, meaning that there was no family history of MTC. The exact etiology, or cause, of sporadic MTC is not fully understood.
The remianing 20% of cases of MTC are hereditary, meaning that the disease occurs due to genetic mutations that are inherited from family members. These inherited forms of MTC usually occur at a younger age (childhood or early adulthood) and can be categorized as one of 3 main syndromes: Multiple Endocrine Neoplasia 2A (MEN 2A), Multiple Endocrine Neoplasia 2B (MEN 2B), and Familial MTC (FMTC).
MEN 2A
Patients MEN 2A tend to have MTC, along with additional growths (parathyroid hyperplasia) or tumors in the parathyroid and adrenal glands. One example is pheochromocytomas, which are rare, hormone-secreting tumors in the adrenal gland that produce epinephrine and norepinephrine, causing symptoms such as sweating and headaches, among others.
MEN 2B
Patients MEN 2B tend to have MTC and pheochromocytomas, as well as benign growths of nerve tissue within the oral cavity or elsewhere, called mucosal neuromas. Medullary thyroid carcinomas related to MEN 2B are often more aggressive.
Familial Medullary Thyroid Cancer
Patients with FMTC present with cancer only in the thyroid and/or associated metastatic lymph nodes. FMTC is not associated with any other tumors or altered hormonal production, as are MEN 2A and MEN 2B.
RET Proto-oncogene Mutations
Genetic mutations in the RET proto-oncogene are known to be the most prevalent risk factor in the development of MTC. These mutations occur in both hereditary and sporadic MTC. If this mutation is detected, screening for other related tumors (such as those present in MEN 2A and MEN 2B) should be performed. The presence of RET proto-oncogene mutations is associated with both an earlier age of presentation and a more aggressive disease.
Learn more about genetic testing in thyroid cancer.
Signs & Symptoms
Thyroid cancers are usually detected by patients or doctors when they feel a lump in the neck or when an imaging test for an unrelated condition shows a lump in the thyroid gland. Other rare signs and symptoms of thyroid cancer include:
- A lump or bump somewhere else in the neck: A metastatic lymph node with a biopsy showing thyroid cancer is a rare way that thyroid cancer can be detected.
- Change in voice: Unlike benign tumors in the thyroid gland, thyroid cancers can invade the nerves to the voice box (larynx) or even adjacent structures such as the trachea and esophagus. This could lead to a hoarse voice or difficulty breathing.
- Difficulty with swallowing (dysphagia): If thyroid tumors become very large (or invade surrounding structures), they can cause difficulty with swallowing.
It is important to note that a patient could have one or more of these symptoms and NOT have thyroid cancer. There are several non-cancerous causes of the same symptoms. That is why it is important for patients to go see a doctor if they are experiencing any of these symptoms.
