What Is a Thyroid Gland?
The thyroid is an endocrine organ shaped like a butterfly and located inside the lower side of the front of the neck. It controls metabolism and helps release thyroid hormones that help in various body functions like managing the heart rate, body temperature, blood pressure, and weight.
What Is a Thyroid Cancer?
Cancer related to the thyroid develops when the cells start to change shape and size and sometimes function. It converts into a tumor when enough cells have mutated. It is treatable if caught in the early stages.
What Are the Types of Thyroid Cancer?
According to research, the following types have been mentioned:
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Papillary Thyroid Cancer - It is the most common type and grows slowly and has a better prognosis.
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Follicular Thyroid Cancer - This can affect the lymph nodes and blood vessels.
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Medullary Cancer - This can be diagnosed in the early stages due to calcitonin production, which is checked during routine blood tests.
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Anaplastic Thyroid Cancer - It is rare but aggressive in nature. It is difficult to treat this type of cancer.
What Is Medullary Thyroid Cancer?
Of the four different types of thyroid cancer, the most common ones are the follicular and papillary types. Medullary thyroid carcinoma (MTC) is a rare type of thyroid cancer. The thyroid gland consists of a neuroendocrine cells called parafollicular C cells, the multiplication of which results in medullary thyroid carcinoma. Derived from the neural crest cells, these C cells are responsible for the synthesis of Calcitonin, which is needed for the regulation of calcium in the body.
What Are the Forms of Medullary Thyroid Cancer?
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Sporadic Medullary Thyroid Cancer:
This is also called the non-hereditary form and is the most common, accounting for about three-fourths of medullary thyroid cancers. This form of medullary thyroid cancer is prevalent among older adults and does have a familial origin.
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Hereditary Medullary Thyroid Cancer:
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As the name suggests, this form of medullary thyroid cancer runs in families. This inherited form of medullary thyroid cancer is of autosomal dominant type. That is, the chances of inheritance are 50 %. It is further divided into the following:
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MEN2A, also known by the name Sipple's syndrome. MEN stands for multiple endocrine neoplasias.
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MEN2B.
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Inherited MTC with no endocrine abnormality.
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What Are the Causes of Medullary Thyroid Cancer?
As formerly stated, medullary thyroid cancers arise from genetic abnormalities concerning the parafollicular C cells of the thyroid gland. However, the cause of such abnormality is not clearly understood.
What Are the Symptoms of Medullary Thyroid Cancer?
In the case of medullary thyroid cancer, the exhibition of symptoms is rare and minimal. Most patients with medullary thyroid carcinoma do not exhibit any symptoms. Even the most prevalent symptoms of thyroid cancer, like fatigue and increased or decreased levels of thyroid hormones, are not evident in this type of cancer.
One important symptom of medullary thyroid cancer includes the presence of a painful lump in the neck region. The lump initially has its origin inside the thyroid tissue, which then gradually grows to reach out of the thyroid tissue. In a majority of individuals, the lump is surrounded by healthy thyroid tissue. For this reason, the swelling is not clearly evident, which makes the diagnosis of medullary thyroid cancer difficult. Although a neck lump is common with all thyroid cancers, in medullary thyroid carcinoma, the lump is tender. This is an important distinctive feature of medullary thyroid cancers.
A significant characteristic of advanced forms of medullary thyroid cancer is the occurrence of diarrhea. This is attributed to the increased level of calcitonin and prostaglandins.
It is not necessary that these symptoms are always indicative of medullary thyroid cancer, and also, these cancers do not need to be always symptomatic. A lump seen or felt in the thyroid can be due to an infection or a goiter, which need not be cancerous. Therefore, reaching out to a healthcare provider regarding any abnormality is always needed to rule out or treat medullary thyroid cancers.
In general, thyroid cancer may show the following symptoms in the patient:
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Swallowing difficulty.
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Breathing difficulty.
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Anonymous cough that is constant.
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Voice changes like hoarseness.
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A lump that grows fast in the front of the neck.
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Radiating pain from neck to ears.
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Swollen glands without pain in the neck.
What About Lymph Node Involvement in Medullary Thyroid Cancers?
As far as lymph node involvement is concerned in medullary thyroid cancers, the frequency of spread is high. There is the involvement of both lymph nodes pertaining to the thyroid gland and the neck at an early stage. Unlike other thyroid cancers, the neck lymph nodes are not infrequently affected in medullary thyroid cancers. Also, involvement of neck lymph nodes is seen even in small medullary thyroid carcinomas.
What Increases the Risk of Developing Medullary Thyroid Cancer?
1. Gender and Age:
Women are three times more prone to develop the sporadic form of medullary thyroid cancer than men. However, in the case of the hereditary type, the incidence rate for men and women is equal. Although individuals can develop medullary thyroid cancer at any age, most of the diagnosis happens in women around their 40s and 50s. In men, the typical age of occurrence is 60 to 70.
2. Hereditary:
Familial history of medullary thyroid cancer puts the individual at risk of developing medullary thyroid cancer. An inherited form of medullary thyroid cancer runs in families. Individuals with medullary thyroid cancer have a 50 percent chance of transmitting the disease to their offspring.
3. Genetic Factors:
Abnormalities in the RET gene of an individual also increase the chance of developing medullary thyroid cancer.
4. Medical History:
The following conditions are also involved in risk factors:
a. Cowden disease.
b. History of multiple endocrine neoplasia type 2.
c. Pheochromocytoma.
d. Pancreatic endocrine malignancies.
e. Hyperparathyroidism.
Unlike other forms of thyroid cancers, radiation exposure does not increase the chance of developing MTC. Also, smoking and alcohol are not considerable risk factors in terms of medullary thyroid cancer.
How Can Medullary Thyroid Cancer Be Diagnosed?
Diagnosis of medullary thyroid cancer is difficult because of its nature of origin. The lump starts initially within and then progresses to the outside, which poses difficulty in diagnosis. Also, this type of thyroid cancer does not manifest symptoms like other types of thyroid cancer.
When you visit your physician, initially, they will ask questions regarding family history, symptoms, and medical history, followed by a physical examination where you will be examined for lumps in the neck or any other swellings.
Then you will be sent for biopsies, blood tests, and imaging tests. The following are the testing methods employed in the diagnosis of MTC:
1. Genetic Testing:
Genetic testing may also be done depending on your family history.
2. Biopsy:
A fine-needle aspiration biopsy of the thyroid or the lump or swelling can be done to come to a definitive diagnosis. Fine-needle aspiration cytology (FNAC) is the preferred biopsy method.
c. Blood Test:
In patients where FNAC indicates a chance for medullary thyroid cancer, the level of calcitonin, calcium, and carcinoembryonic antigen (CEA) in the blood is measured, which is usually increased in people with MTC. Also, less often, the level of metanephrine or normetanephrine in the blood or urine is measured.
d. Imaging Tests:
An ultrasound will be done to check for soft tissue lesions if required. Radioiodine scan to check for the radiation related to the thyroid or other body parts. CT scans and PET scans can also be preferred to locate and study thyroid cancer.
Based on all these test results, your physician will come to a final diagnosis of cancer or not.
How Can Medullary Thyroid Cancer Be Treated?
If diagnosed in the early stages, medullary thyroid cancer has an excellent prognosis. However, with no or minimal symptoms, diagnosis is difficult. The physician decides the treatment based on the location and extent of cancer to give a better prognosis and best possible treatment depending on the individual.
The management primarily involves surgery. The following are the treatment modalities employed in the treatment of medullary thyroid cancer:
1. Surgery:
Medullary thyroid cancer is managed using surgery more commonly. If complete removal of the thyroid gland is done, it is called a thyroidectomy. Partial removal of the thyroid gland is called a lobectomy. Sometimes, there can be the removal of adjacent lymph nodes and tissues due to the involvement of the tumor. However, in most medullary thyroid cancer cases, total thyroidectomy and removal of central compartment lymph nodes are advised owing to the increased frequency of spread to neck lymph nodes.
2. Thyroid Hormone Therapy:
Thyroid hormone pills can be consumed after the complete removal of thyroid glands. These pills also help limit the growth and progression of leftover cancerous cells. The mode of action is to lower the levels of thyroid-stimulating hormone (TSH).
3. Palliative Treatment:
If cancer has spread beyond the thyroid tissue, removing the entire cancer mass is not recommended. Instead, the thyroid gland is removed, followed by palliative care. The following palliative treatment methods are preferred in the advanced stages of cancer:
a. External Beam Radiation (X-Ray Therapy) - In this, the radiation is used to kill the cancer cells. The procedure follows for several weeks, and all precautionary measures are taken to avoid radiation exposure to other parts of the body.
b. Chemotherapy - Chemotherapy utilizes chemicals or medicines to kill cancer cells or limit their growth and progression. Two recently approved chemotherapeutic agents, Vandetanib and Cabozantinib, have good efficacy on medullary thyroid cancers.
c. Targeted Therapy - This is a newer treatment strategy where a pill is consumed to limit the growth or destroy cancer cells, and there are fewer side effects than chemotherapy.
What Is the Survival Rate in Medullary Thyroid Cancers?
Prognosis with medullary thyroid cancers is dependent on the stage of cancer at the time of diagnosis. Individuals diagnosed at the early stages have a reasonable prognosis rate compared to those diagnosed in the advanced stages. This is because palliative care is only advised in the later stages, and complete removal of the tumor is impossible.
The rate and frequency of lymph node involvement seen in medullary thyroid cancers also impact survival rates. For example, the survival rate, which accounts for 90 % of individuals with medullary thyroid carcinoma that involves only the thyroid gland, drops to 70 % in people whose neck lymph nodes are involved.
The recurrence rate of medullary thyroid cancer is also less if the tumor is completely removed. For example, after 5 to 7 years of surgery, only 4 % of people develop recurrent growth of medullary thyroid cancer.
Conclusion:
Medullary thyroid cancer has various forms and can be managed if diagnosed during the early stages. If you have a family history of medullary thyroid cancer, it is essential to have adequate screening. Also, before planning for pregnancy, genetic counseling is necessary to limit the chances of transferring MTC to your child. Consult your physician if you have any doubts or develop any mentioned symptoms. Online medical platforms have made the consultation process very easy. Hence, you can contact a specialist at the ease of your home.
