Medullary thyroid cancer is the third most common type of thyroid cancer. This article will discuss common medullary thyroid cancer symptoms and treatments as well as medullary thyroid cancer diagnosis and prognosis.
Medullary tumors are the third most common of all thyroid cancers. They make up about 3% of all thyroid cancer cases.
But what are some common medullary thyroid cancer symptoms?
papillary thyroid cancer and follicular thyroid cancer that arise from thyroid hormone producing cells, medullary thyroid cancer originates from the parafollicular cells (also called C cells) of the thyroid.
These C cells make a different hormone called calcitonin, which has nothing to do with the control of metabolism the way thyroid hormone does.
This cancer has a much lower cure rate than does the well-differentiated thyroid cancers (papillary and follicular), but cure rates are higher than they are for anaplastic thyroid cancer.
Overall, 10-year survival rates are 90% when all the disease is confined to the thyroid gland; 70% with spread to cervical lymph nodes; and 20% when spread to distant sites.
Clinically, these tumours are characterised by rapid growth and therefore often manifest as palpable masses. Lesions can be quite large at presentation.
An MCB typically arises from supporting stromal cells of the breast 3. The World Health Organization (WHO) criteria for diagnosis are “a well circumscribed carcinoma composed of poorly differentiated cells with scant stroma and prominent lymphoid infiltration”.
Large pleomorphic nuclei prominent nucleoli and high mitotic activity may be seen. The histologic appearance of medullary carcinoma can mimic that of poorly differentiated intra ductal carcinoma not otherwise specified. Areas of associated necrosis may be present.
There are two types of MCB:
typical type: has to meet with the following criteria
a) syncytial growth pattern of poorly differentiated tumor cells with a high mitotic rate
b) prominent lymphoplasmacytic reaction with a circumscribed microscopic appearance-inflammatory reaction must involve 75% of the periphery and must be present diffusely throughout the substance of the tumor
c) no glandular or fatty breast tissue should be found within the invasive portion of the tumour.
atypical type: resembles the usual classic case; it must have at least 75% syncytial growth but does not have the other two features (circumscription and lymphoplasmacytic infiltration).
Many medullary carcinomas tend to be oestrogen and progesterone receptor negative.
Characteristics of Medullary Thyroid Cancer
- Occurs in 4 clinical settings (see below) and can be associated with other endocrine tumors
- More common in females than males (except for inherited cancers)
- Regional metastases (spread to neck lymph nodes) occurs early in the disease
- Spread to distant organs (metastasis) occurs late and can be to the liver, bone, brain, and adrenal medulla
- Not associated with radiation exposure
- Usually originates in the upper central lobe of the thyroid
- Poor prognostic factors include mean older than 50 years old, distant spread (metastases), and when seen in patients with other endocrine tumors due to MEN II-B syndrome.
- Residual disease (following surgery) or recurrence can be detected by measuring calcitonin (a hormone that should be measured every 4 months for the first few years and then every 6 months for the rest of your life)
Management of Medullary Thyroid Cancer
Thyroid gland has 2 lobes connected by an isthmus.In contrast to papillary and follicular cancers, little controversy exits when discussing how to treat medullary thyroid cancer.
After assessment and treatment of associated endocrine conditions (such as pheochromocytomas if present) by an endocrinologist, all patients should receive total thyroidectomy, a complete central neck dissection (removal of all lymph nodes and fatty tissues in the central area of the neck), and removal of all lymph nodes and surrounding fatty tissues within the side of the neck where the tumor was present.
A diagram of thyroid operations are covered in greater detail (with drawings) in our article about the various thyroid surgery options.
Radioactive Iodine and Medullary Thyroid Cancer
Although thyroid cells have the cellular mechanism to absorb iodine, medullary thyroid cancer does not arise from this type of thyroid cell.
Therefore, radioactive iodine therapy is not useful for the treatment of medullary thyroid cancer. Similarly, if medullary cancer spreads to distant sites, it cannot be found by iodine scanning the way that distant spread from papillary or follicular cancer can.
Typically seen as a rounded – ovoid mass with ill-defined or circumscribed margins at mammography. There can be varying degrees of lobulation while calcification is usually not a feature.
The mass can be either homogeneously hypo-echoic or hypo-echoic with mild heterogeneity 1-2. Enhanced through transmission may be present 2. The level of hypo-echogenicity can sometimes be marked 8.
May show diffuse enhancement post contrast.
What Kind of Long-term Follow Up Is Necessary?
In addition to the usual cancer follow up, patients should receive a yearly chest x-ray as well as calcitonin levels.
Serum calcitonin is very useful in follow up of medullary thyroid cancer because no other cells of the body make this hormone.
A high serum calcitonin level that had previously been low following total thyroidectomy is indicative of recurrence.
Under the best circumstances, thyroid surgery will remove all of the thyroid and all lymph nodes in the neck that harbor metastatic spread.
In this case, post-operative calcitonin levels will go to zero. This is often not the case, and calcitonin levels remain elevated, but less than pre-operatively.
These levels should still be checked every 6 months, and when they begin to rise, a more diligent examination is in order to find the source.
The prognosis tends to be better than for intraductal carcinoma in situ (NOS).