The lymph nodes of the body function similar to a charcoal filter system. Thyroid cancer cells can get caught within the filter but the body has no means of removing the captured cells. The cells are basically then stuck in the lymph node and they begin to grow in that location. The lymph node areas of the neck can be divided into three basic areas:
- The central neck (the lymph nodes beneath and surrounding the thyroid gland, breathing tube (trachea) and swallowing tube (esophagus)
- The anterolateral neck (the side of the neck along the outside portion of the major veins and arteries of the neck [internal jugular vein and carotid arteries]
- The posterolateral neck (the very back side of the neck [rarely involved by thyroid cancer])
Thyroid cancer surgery must address the lymph node areas that are known to contain cancer as well as those that are at significant risk of having thyroid cancer. This type of the thyroid cancer surgery is termed comprehensive compartmental dissection.
Comprehensive does not mean destructive by any means. These lymph node surgeries remove lymph nodes and fatty tissue and spare all major nerves, blood vessels and muscles. They have essentially no cosmetic or functional impact other than a fine scar line.
The two types of comprehensive compartmental dissections which we will discuss here are:
- Central compartment dissection
- Modified radical neck dissection (or anterolateral neck dissection)
Thyroid Cancer Surgery for Central Compartment Lymph Nodes
The removal of the lymph nodes of the central neck can be performed initially when the thyroid gland is removed in the treatment of the thyroid cancer or following the initial surgery in the less common circumstances when thyroid cancer recurs or persists. The central compartment lymph node surgery spares all critical structures including the nerves to the voice box and all parathyroid glands not directly involved by cancer. Central compartment dissection extends from the carotid arteries on both sides of the neck, below to the blood vessels of the upper chest, and above to where the blood vessel of the upper portion of the thyroid gland begins off of the carotid artery (called the superior thyroid artery).Thyroid cancer surgery of the Central compartment
- The central compartment lymph nodes are at risk of containing cancer in up to 50% of patients. That risk increases with the size of the papillary thyroid cancer. Even prior to surgery, most central compartment lymph nodes can be well examined with high quality ultrasound to determine if they are cancerous. Here, the arrow points to an abnormal lymph node seen on ultrasound next to the thyroid gland before surgery. Abnormal lymph nodes undergo fine needle aspiration (FNA) examination to determine whether cancer is present. Some lymph nodes which lay immediately underneath the thyroid gland cannot be seen until the time of surgery and required a skilled surgeon to identify them and can then be confirmed during the surgery by a process called frozen section pathology.
- If central compartment lymph nodes are found at any time in a patient’s lifetime, an expert thyroid cancer surgeon who does this surgery routinely is needed to remove the lymph nodes in the central compartment, on both sides) and spare the nerves to the voice box and the critical glands that control calcium (parathyroid glands).
For papillary thyroid cancers which are greater than one inch (2.5 cm) or have grown outside of the capsule of the thyroid, removal of the lymph nodes of the central compartment on the side of the cancer should be done routinely since:
- The nerve to the voice box (recurrent laryngeal nerve) has already, by necessity from the thyroid surgery itself, been significantly identified along most of its course and another surgery on the same side would be more difficult because of scarring and this subsequent surgery would put the nerve to the voice box at high risk for injury.
- In Medullary thyroid cancer the central compartment lymph nodes are removed routinely on both sides of the central compartment.
- In hereditary medullary thyroid cancer patient’s family members (who have been determined to have only the genetic mutation for the medullary thyroid cancer), (but no suspicion of medullary thyroid cancer!), central compartment dissection need not be performed.
- There are known genetic mutations of medullary thyroid cancer that allow surgeons to understand the relative risk of these hereditary thyroid cancers to spread to lymph nodes and distant sites.
- In Hurthle cell cancer (or carcinoma) is a rare but potentially very aggressive variant of follicular thyroid cancer. It differs significantly from follicular thyroid cancer in that hurthle cell cancers have a very high risk of spreading to neck lymph nodes. In hurthle cell cancers, central compartment lymph nodes should always be removed on the side of the cancer since they are at very high risk for lymph node metastases unlike follicular thyroid cancers. A fine needle aspiration consistent with a hurthle cell adenoma should be removed, on one side, as if it were a hurthle cell cancer. Pathology at the time of surgery can examine for spread of hurthle cell cancer to these lymph nodes therefore providing the diagnosis of hurthle cell cancer (carcinoma). Hurthle cell adenomas will never spread to lymph nodes. This is one straight forward manner to tell the difference between hurthle cell cancer and hurthle cell adenoma at pathology during surgery if the central compartment lymph nodes are involved.
- Thyroid cancer surgery for poorly differentiated or anaplastic thyroid cancers undergoing thyroid cancer surgery, the central compartment lymph nodes at least on the side of the thyroid cancer should be comprehensively removed.
Modified radical neck dissection (or anterolateral neck dissection)
Just the presence of enlarged lymph nodes does not mean thyroid cancer has spread and does not require additional surgery. A procedure called a modified radical neck dissection (or anterolateral neck dissection or comprehensive neck dissection), in untreated patients, should only be performed in instances of ultrasound with fine needle aspiration confirmed thyroid cancer spread to lymph nodes on the side of the neck
- Just the presence of enlarged lymph nodes does not mean thyroid cancer has spread and does not require additional surgery
- A procedure called a modified radical neck dissection (or anterolateral neck dissection or comprehensive neck dissection), in untreated patients, should only be performed in instances of ultrasound with fine needle aspiration confirmed thyroid cancer spread to lymph nodes on the side of the neck
- The thyroid cancer surgery for spread of cancer to lymph nodes of anterolateral neck is not the same modified radical neck dissection as for other cancers that occur in the neck. Thyroid cancer spreads to particular areas of the neck called levels. Removing just some of the lymph nodes has been called “cherry picking” and is the wrong surgery! A thyroid cancer surgery expert trained surgeon and experienced to perform modified radical neck dissections specifically for thyroid cancer is needed to prevent recurrent or persistent disease.
- The modified radical neck dissection, in skilled hands, spares all critical nerves, muscles, and blood vessels which are not directly involved with cancer (very rarely are critical structures involved by thyroid cancers except the most advanced aggressive cancers [Unless you are above 50 years of age, you almost certainly do not have an aggressive cancer. Even if you are above 50 years of age, aggressive thyroid cancers are rare] ). It is an approximately 40 minute surgery that removes lymph nodes and fatty tissue.