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The Wonderful World of Medullary Thyroid Cancer: Why Nausea and Diarrhea May Be Warning Signs.
Medullary thyroid cancer (MTC) is a tumor that arises from the accessory follicular cells of the thyroid gland, which produce the important hormone calcitonin. According to statistics, medullary thyroid cancer is the third most common type of thyroid cancer, accounting for only 3% of all thyroid cancer cases. Medullary thyroid cancer has been studied in detail since 1959. About 25% of cases have a genetic background, mainly caused by mutations in the RET oncogene.
When medullary thyroid cancer occurs alone, it is called sporadic medullary thyroid cancer.
Medullary thyroid cancer is common in patients with multiple endocrine neoplasia type 2A and type 2B. When it is caused by an inherited gene and there are no other endocrine tumors, it is called familial medullary thyroid cancer.
Symptoms and Signs
The main clinical symptom of MTC is diarrhea; occasionally patients experience flushing. These two symptoms are particularly prominent in the setting of liver metastasis and may sometimes be the first signs of the disease.
The flushing phenomenon is indistinguishable from Carcinoid Syndrome. Flushing, diarrhea, and itching in MTC are all caused by elevated levels of the calcitonin gene product.
In contrast, the flushing and diarrhea observed in Caronide syndrome are due to elevated serotonin. Medullary thyroid cancer may also cause thyroid nodules and swollen lymph nodes in the neck and may spread to the lymph nodes in the neck, central lymph nodes in the chest, liver, lungs, and bones, although spread to the skin or brain is less common. .
Genetics
The RET proto-oncogene is located on chromosome 10, and mutations lead to abnormal expression of receptor tyrosine kinase protein. Germline mutations in this gene are critical for the regulation of cell growth and development and are responsible for nearly all cases of familial medullary thyroid cancer.
Familial medullary thyroid cancer (MEN2) accounts for approximately 25% of all medullary thyroid cancers. 75% of cases are "sporadic" MTC with no apparent family history.
Diagnosis
The diagnosis of medullary thyroid cancer is mainly through fine needle aspiration of the thyroid lesion. Microscopically, proliferation of amyloid matrix and accessory follicular cells can be seen. A recent systematic review analyzing the diagnostic accuracy of basal and stimulated calcitonin showed that these tests have high accuracy but are at risk of bias due to design flaws. Overall, the value of routine calcitonin testing in medullary thyroid cancer remains uncertain.
Treatment methods
Surgery and radiation therapy are the main treatments for medullary thyroid cancer. Plasma mesenchymal hormone levels need to be checked before surgery to assess the presence of pheochromocytoma, as 25% of patients with medullary thyroid cancer have a genetic history of MEN2A syndrome.
Total thyroidectomy and bilateral neck dissection are the standard approach for the treatment of medullary thyroid cancer.
During treatment, external radiation therapy is recommended for high-risk patients to prevent regional recurrence even after optimal surgical management. Studies have shown that patients who received radiation therapy had better disease control than the control group.
Prognosis
Depending on the source, the 5-year overall survival rate for medullary thyroid cancer is approximately 80%-86%, while the 10-year survival rate is 75%. Of course, the survival rates at different stages vary greatly, and the 5-year survival rate of the first stage can reach 100%. In addition, the prognosis is related to the changes in calcitonin levels after surgery. Some studies have shown that the doubling time of calcitonin (CDT) is an important indicator for predicting the survival rate of medullary thyroid cancer.
During the diagnosis of medullary thyroid cancer, patients may experience symptoms such as nausea and diarrhea, which may be important warning signs sent to them by the body. How can we respond correctly to these signs in the early stages, and what impact will it have on the patient's prognosis?
