Thymectomy

Overview of Thymectomy

A thymectomy is a medical operation that involves taking out the thymus gland, a small organ that is part of your immune system. This type of operation is key to treat several conditions, including different types of thymic tumors (like thymomas, thymic carcinomas, and thymic neuroendocrine tumors) and a condition called myasthenia gravis (MG), which can cause muscle weakness.

The first thymectomy was done by accident during thyroid surgery for a condition called Graves’ disease. It wasn’t until Blalock and his team showed how useful thymectomy could be in treating MG, even for patients who didn’t have thymomas, that this surgery became more commonly used.

Since then, there have been many advancements in how thymectomies are performed. The traditional method involved an incision down the center of the chest (called a median sternotomy or transsternal approach), which is still considered the standard way to perform this surgery.

However, doctors have also developed less invasive methods, including partial upper sternotomy, transcervical (across the neck) approaches, video-assisted thoracoscopic surgery, and surgery using robotic assistance. It’s been shown that these minimally invasive methods have better results, including shorter hospital stays and fewer complications.

Before doing a thymectomy, doctors use imaging tools (like X-rays or MRIs) to figure out the size and extent of the tumor and determine the best treatment plan. They also assess lung function, which is particularly important if the surgery requires to operate on one lung at a time (a procedure known as single-lung ventilation).

This article explores the changing role of thymectomy, describing when it’s needed, how it’s performed, and the expected outcomes.

Anatomy and Physiology of Thymectomy

The thymus is a two-sectioned organ located in the upper chest, surrounded by the breastbone, the pericardium (a sac enclosing the heart), the diaphragm (a muscle beneath the lungs that helps with breathing), and a line connecting the chest opening to the fourth backbone in the chest. Among other elements in its surroundings are fat and lymph nodes. The thymus, which starts developing from a particular part of the early embryo, keeps growing till puberty. After that, it begins to shrink, and fat begins to replace some of its tissue annually by about 1% to 3%. However, despite this shrinking process, the thymus can keep functioning throughout a person’s life.

The thymus can reach up to the thyroid gland (a gland in the neck that produces hormones), and sometimes, parts of it can be found in places where it’s not typically seen, most commonly in the chest’s fat.

The blood supply to the thymus mainly comes from the inferior thyroid artery and the inner breastbone arteries, with additional blood supply from the pericardiophrenic and intercostal arteries. Its vein and lymphatic systems are similar to its blood supply routes. The thymus is designed in a way that it has lobules divided by a fibrous capsule. This structure allows it to hold many immature lymphocytes (a type of white blood cell) in the outer cortex and more mature ones in the inner medulla.

The thymus plays an essential role in building immunity. Immature lymphocytes from bone marrow (a tissue within bones that makes blood cells) transfer to the thymus, where they mature and form functional T-cells. These T-cells are essential in activating our immune responses against diseases. However, the thymus also has to prevent excessive immune responses that could harm our body. To achieve this balance, a selection of necessary lymphocytes occurs in the outer cortex and the inner medulla, ensuring beneficial cells stay while harmful cells are removed.

A condition called Myasthenia Gravis (MG) frequently occurs with the thymus. This is a disease where the body’s immune system mistakenly attacks itself, causing muscle fatigue. Thymomas, tumors often found in the thymus, are also sometimes associated with MG.

Furthermore, there’s a known phenomenon called thymic involution, associated with the aging of the immune system. This process, starting early in life and accelerating after puberty, involves decreasing thymus cells and increasing fat tissue in the thymus. These changes appear to be associated with an increase in steroid hormones, particularly sex hormones. Notably, some residual thymus tissue can persist in the body and still contribute to the immune system even later in life, highlighting its ongoing importance in maintaining the body’s health.

Why do People Need Thymectomy

Thymectomy, or the removal of the thymus gland through surgery, is done to manage different tumors and conditions that involve the thymus and the anterior mediastinal structures nearby. Anterior mediastinal structures refer to tissues and organs located in the front part of the area between the lungs. Despite technological advancements in imaging, managing conditions that affect these structures can be quite complicated due to the variety of underlying issues that can occur there.

Reasons for surgery:

Tumor-related reasons

* Thymomas
* Thymomas, are the most common tumors in the area between the lungs. They are one of the main reasons why thymectomy might be recommended. The preferred treatment for both non-invasive and invasive thymomas is surgical removal. However, there could be worries of disease spread during invasive diagnostic procedures like biopsies. Therefore, when the presence of a thymoma is strongly suspected, upfront surgery is favored to avoid further complications.
* Thymic carcinomas
* These aggressive cancerous tumors usually require thymectomy. This is often combined with other treatment methods like chemotherapy and radiation.
* Thymic neuroendocrine tumors
* Rare tumors such as carcinoid tumors may need thymectomy to treat localized disease and decrease symptoms.
* Thymic cysts
* While thymic cysts are benign (not cancerous), if they cause symptoms, are getting bigger, or show signs of being cancerous, they may need to be surgically removed.
* Other malignant conditions
* Other malignant conditions, including lymphomas and germ cell tumors, can occur in the anterior mediastinum. These are generally managed medically or with radiation; surgical intervention is typically reserved for diagnosing the condition or for palliative purposes (relieving symptoms without curing the disease).

Non-tumor-related reasons

* MG
* Thymectomy is a well-established treatment for Myasthenia gravis (MG), especially in the presence of thymomas. In cases of generalized disease that doesn’t respond to medicine, thymectomy is indicated. Evidence suggests that this improves long-term outcomes and reduces dependency on medication. Juvenile and ocular MG are additional reasons for thymectomy.
* Thymic hyperplasia
* If there is significant thymic overgrowth causing mass effects or complicating associated autoimmune disorders, surgical removal may be necessary.
* Ectopic parathyroid glands
* Sometimes, ectopic parathyroid tissue located within the thymus needs to be removed, particularly in cases of poorly managed hyperparathyroidism (overactive parathyroid glands).

In certain unusual cases, thymectomy might be considered for autoimmune diseases linked with thymus abnormalities like systemic lupus erythematosus or pure red cell aplasia. A partial thymectomy is occasionally performed for diagnostic purposes, especially when a lymphoma is suspected and a tissue diagnosis is required.

Challenges in Diagnosis and Management

Diagnosis and managing diseases in the anterior mediastinal region often involves finding a balance between getting a definite diagnosis and minimizing unnecessary surgery. A technique named core-needle biopsy is the gold standard for diagnosing advanced or nonresectable lesions, but it comes with risks such as bleeding, developing a pneumothorax (collapsed lung), and in the case of thymomas, leading to spread of the disease due to seeding of the tumor during the procedure. Hence, biopsy is recommended only for advanced or diseases that cannot be removed. When a thymoma is suspected and can be removed, a biopsy is typically not done and directly removing the lesion is favored to avoid complications.

Minimally Invasive Approaches

Modern surgical techniques, such as video-assisted thoracoscopic surgery and robotic-assisted thymectomy, provide new options for thymectomies. These methods are valid alternatives to traditional open surgeries and are linked with lesser complications, short hospital stays, and faster recovery times which makes them increasingly the preferred option in suitable cases.

When a Person Should Avoid Thymectomy

Thymectomy, a surgery to remove the thymus gland, can be a crucial treatment for certain conditions including thymomas (tumors of the thymus) and Myasthenia Gravis (MG, a disorder causing muscle weakness). However, some health issues or technical factors might make the operation more risky, or require changes to the way the operation is done. These issues can be grouped into three categories: general surgical risks, concerns specific to thymectomy, and factors related to minimally invasive approaches.

Some general surgical risks include:
– Being too weak or sick to handle general anesthesia. This is often seen in patients with severe heart or lung disease, or those who are extremely frail.
– acute instability due to conditions like sepsis (a life-threatening illness caused by your body’s response to an infection), unmanageable arrhythmias (irregular heartbeats), or very low blood pressure. Such patients are not suitable for an elective thymectomy.
– Having ongoing bleeding disorders or taking blood thinners that can’t be safely stopped for the operation. This can increase the risk of bleeding during and after surgery, making surgery contraindicated until these issues can be addressed.

Issues more specific to thymectomy itself include:
– When a thymus tumor is too advanced and has spread into major blood vessels, minimally invasive techniques won’t work and fully removing the tumor may be impossible. In these situations, other solutions, like palliative care (relieving symptoms but not curing) or primary chemotherapy (cancer drug treatment), might be needed.
– If the thymus cancer has spread to distant parts of the body (metastasized), surgery is unlikely to cure it. In these cases, drug treatment is the priority.
– Some MG patients who have their symptoms effectively managed with medication might not see significant benefits from thymectomy, especially if their condition isn’t due to an existing thymoma.
– Pregnancy isn’t a hard-stop barrier to thymectomy, but it’s usually delayed until after the baby is born unless there’s an urgent medical reason, such as rapidly growing thymomas causing symptoms due to pressure on adjacent structures.

For minimally invasive surgeries, some specific factors include:
– A thymus tumor that’s grown extensively into critical areas like major blood vessels.
– In minimally invasive surgeries, surgeons often need to ventilate (inflate) one lung at a time. If a patient can’t tolerate this, a different surgical approach might be needed.
– Past chest surgeries or radiation could have scarred the area, making minimally invasive surgeries more challenging and riskier.

There are also some relative contraindications including, non-surgical masses such as thymic cysts, lymphomas, and other masses, severe MG symptoms like bulbar weakness or respiratory failure that require preoperative treatment, and the presence of thymic tissue outside its usual location, which can complicate surgical planning, particularly with minimally invasive approaches.

Equipment used for Thymectomy

In an open surgical approach, such as through the chest (median sternotomy) or neck (transcervical approach), the following equipment is needed:

• A sternal saw: this is a special type of saw used to cut through the sternum (the breastbone).
• A sternal retractor: this tool is used to hold the sternum open during surgery.
• Energy devices like electrocautery, bipolar, ultrasonic: these tools use different types of energy to cut or seal tissue.
• Staplers: used to close up incisions or wounds after surgery.
• Sternal wires: these are used to secure the sternum back together after it’s been cut open during surgery.

Thymectomy, a surgery to remove the thymus gland, done via minimally invasive technique (VATS means video-assisted thoracic surgery) requires:

• Surgical hooks to lift up the sternum.
• A 30-degree camera: this allows the surgeon to see inside your chest during the surgery.
• Electrocautery or ultrasonic energy devices: these tools use energy to cut or seal tissue.
• Standard endoscopic instruments: these tools are used in minimally invasive surgeries and are inserted through small incisions.
• Endoscopic staplers: used to close up incisions or wounds after surgery.
• An endo catch bag: this bag is used to collect and remove tissues during surgery.

For a robotic-assisted thymectomy, which is performed with the help of a surgical robot, the following equipment is needed:

• DaVinci surgical system: a common robotic system used in surgeries that allows the surgeon to control the robot’s arms during the procedure.
• A high-definition stereoscopic camera: provides a 3D view inside your body to help guide the surgery.
• Endoscopic graspers: these are robotic tools used to hold and move tissues during surgery.
• Needle drivers: are robotic tools that hold sutures – threads used to sew up wounds.
• Staplers: used to close up incisions or wounds after surgery.
• Endocatch bag: this bag is used to collect and remove tissues during surgery.
• Electrocautery devices: these tools use electric energy to cut or seal tissue.

Who is needed to perform Thymectomy?

When doing an open surgery approach known as median sternotomy or a transcervical approach, the surgery team includes some important people:

* The main doctor doing the surgery or primary surgeon
* An anesthesiologist, a special kind of doctor who helps you sleep and stay comfortable during the surgery
* A nurse trained to help the anesthesiologist, also known as a nurse anesthetist
* A surgical technologist who helps prepare and maintain the tools the surgeon uses.

A procedure known as thymectomy, which is done using a special camera called video-assisted thoracoscopic surgery, needs the same team members:

* Primary surgeon
* Anesthesiologist
* Nurse anesthetist
* Surgical technologist

And if the thymectomy is done using a robotic system, the team is slightly different:

* The primary surgeon
* The anesthesiologist
* The nurse anesthetist
* A specially trained surgical technologist who knows how to handle the robotic system
* An extra person called a surgical assistant who helps by passing instruments to the surgeon when needed.

Preparing for Thymectomy

Preparing for thymectomy, a surgery to remove the thymus gland, includes several steps taken by a team of healthcare experts for the patient’s safety and to make sure surgery outcomes are favorable. This involves a complete health evaluation, disease-specific considerations, and using imaging tools for a detailed examination, especially for conditions like myasthenia gravis (MG, a chronic autoimmune neuromuscular disease causing muscle weakness) and thymus gland tumors.

The doctors carry out a detailed checkup and lab tests to identify symptoms linked to lesions in the anterior mediastinum (the space in the chest where the thymus gland lies) and to detect conditions related to tumors such as MG or lymphoma (a type of blood cancer). Lab tests can include a full blood count and tumor marker tests which help in diagnosis.

Doctors use advanced imagery techniques including computed tomography (CT) scans, magnetic resonance imaging (MRI), and positron emission tomography (PET) scans. This helps in assessing factors like the tumor’s size, its location, and the extent to which it is involving surrounding structures like blood vessels. The imagery techniques help in distinguishing various conditions.

Thymic hyperplasia, a condition where the thymus gland increases in size, often does not show any symptoms and is usually spotted during imaging carried out for unrelated reasons. However, in rare instances, significant enlargement of the thymus gland can lead to acute symptoms. Imaging by itself sometimes might not be enough to differentiate between different conditions.

In cases of MG, it is vital to stabilize the patient before surgery to prevent a severe muscular weakness episode. This might include treatments like plasmapheresis (a procedure that filters the blood), and intravenous immunoglobulin (a blood product used to treat certain conditions in certain cases). Thorough examination should also include lung and heart tests. Even if lung resection (removal of part of the lung) is not indicated, thymectomy can have significant effects on respiratory function, especially for patients with MG. Therefore, additional tests may be required depending on the patient’s overall health condition.

Among children, most chest masses are situated within the mediastinum. These masses can have different causes, including congenital anomalies, infections, or benign and malignant tumors. Many children with such masses don’t show symptoms and medical practitioners often discover these masses unexpectedly during chest X-rays. Identifying the place where the mass is located often involves using the Felson method. That method uses a line drawn from the diaphragm to the chest inlet separated by two critical areas: the anterior and middle mediastinal compartments. Another line, situated 1 cm behind the anterior margin of the vertebral bodies, differentiates the middle and posterior compartments.

In children, advanced imaging is usually better at giving a detailed and accurate diagnosis than routine X-rays. The normal thymus typically appears in the prevascular mediastinum with a certain shape and without exherting pressure on surrounding structures. On CT or MRI images, the thymus presents as a consistent structure with uniform enhancement.

To help reduce the number of unnecessary thymectomies, there’s a predictive model that uses CT and PET-CT parameters and clinical data. It serves as a tool to help distinguish between mediastinal lymphomas and thymomas. The research findings suggest that, if a younger patient has anterior mediastinal masses with higher SUVmax on PET-CT, it’s more probable to be lymphoma than thymoma.

How is Thymectomy performed

Before an operation, it is usually recommended to take certain procedures for the safety and comfort of the patient. This may include inserting a catheter, a small tube inserted into the bladder to monitor urine output. A type of epidural may also be given to help manage pain, and an arterial line may be used to continuously monitor the patient’s vital signs. The patient is also intubated, meaning a tube is inserted into their lungs to aid with breathing, and this is checked for correct placement with a procedure called bronchoscopy.

The operation being described here is a thymectomy, which involves the removal of the thymus, a small organ in your chest. The method chosen by the surgeon depends on factors such as the size of the tumor, where it is located, and how much it has invaded other tissue. Transsternal thymectomy, which involves making a cut down the middle of the chest, is typically used for larger or invasive tumors. Conversely, transcervical (through the neck) and minimally invasive methods like video-assisted thoracoscopic surgery (VATS) and robotic-assisted thymectomy may be preferred for smaller tumors and less invasive conditions.

In a median sternotomy, the patient lies on their back while the surgeon makes a vertical cut down the middle of the chest. The cut is made deep enough to access the thymus, and all thymic tissue is removed. Drains are then placed to remove any fluid after surgery, and the chest is stitched back together.

In the transcervical method, the patient lies on their back with a roll under their neck. An incision is made in the lower neck, and the thymus is carefully removed through this incision. The incision is then stitched back together in layers.

VATS is done while the patient lies on their back and is prepped for surgery. This method is usually done through the patient’s right side, as it may allow for better exposure. The surgeon makes small incisions in the chest and inserts instruments to remove the thymus. After the thymus has been removed, a tube is placed to drain any fluid, and each lung is allowed to re-expand (inflate).

In robotic-assisted thymectomy, the patient lies on their back, with the right side raised using folded blankets or a gel pad. The surgeon controls a robot through a console to perform the surgery. Similar to the VATS procedure, the surgeon makes small incisions in the chest, and the thymus is removed using the robotic arms and an Endocatch bag, a device used to capture the removed tissue. After the thymus is removed, any bleeding is controlled, the right lung is reinflated, and a tube is placed to drain any fluid. The incisions are then stitched or stapled closed.

Regardless of the method used, various considerations need to be taken into account during a thymectomy to ensure the procedure goes as smoothly as possible. This includes gaining the best access to the thymus based on the patient’s anatomy and using single-lung ventilation, which involves deflating one lung to improve the view of the area where the surgeon is working. A right-sided approach is often preferred as it allows for greater visibility and access to certain blood vessels and parts of the thymus, leading to a safer and more efficient operation.

Possible Complications of Thymectomy

During a thymectomy, which is a surgical procedure to remove the thymus gland, certain complications can occur. These may include bleeding and unintentional harm to nearby structures, both of which pose significant risks. Bleeding can occur from small thymus veins or larger blood vessels like the innominate vein, which is a major vein in your chest. Damage to Keynes great vein, a major thymus vein, might lead to severe bleeding. If this happens, the doctor may need to change the surgery from a minimally invasive to a more traditional open surgery technique.

After the surgery, some people might experience a pneumothorax, which is a collapsed lung, or ongoing air leaks. In such scenarios, a medical tube might be needed for extended periods to manage these complications.

Chylothorax, a condition where lymphatic fluid accumulates in the space around the lung, can happen if the surrounding lymphatic tissue gets damaged during the surgery, especially near the thymus poles. During the procedure, damage may also be caused to the pericardium, the sac that covers the heart, and the heart itself or the nearby phrenic nerves. These nerves play a vital role in breathing. Therefore, any damage to them could lead to diaphragmatic dysfunction meaning difficulty in breathing after the surgery.

On top of that, if the thymus is not completely removed during the thymectomy, this can result in continued symptoms in patients with Myasthenia Gravis (MG)—a disorder causing muscle weakness—or the comeback of thymomas, which are tumors originating from the thymus. Hence, it’s crucial for the surgeon to perform a careful surgical dissection to prevent these complications and achieve the best possible outcome.

What Else Should I Know About Thymectomy?

Thymectomy, or the surgical removal of the thymus gland, is crucial to treat various conditions such as thymoma (a tumor in the thymus), myasthenia gravis (MG, a weakness and rapid fatigue of muscles), and other disorders related to the thymus.

This procedure can be done in several different ways, which ranges from traditional open surgeries to newer, less invasive methods. In the past, thymectomy was usually done through a large incision in the middle of the chest (called a median sternotomy), which allowed the surgeon to clearly see the thymus and surrounding areas. However, with recent advancements in medical technology, minimally invasive methods like video-assisted thoracoscopic surgery (VATS) and robot-assisted thymectomy have been increasingly used due to their numerous benefits.

The robot-assisted method of thymectomy presents several advantages over the traditional open surgery. It results in less blood loss during the operation, lowers the chances of having complications after surgery, and shortens the length of stay in the hospital. Studies show that it’s equal to, or even better than, the traditional method in completely removing the thymus, with no remaining signs of the disease on the edges of the removed tissue.

The VATS method has similar benefits too, such as less complications during the operation, reduced recovery time, and effective in treating the diseases. This method is like the robot-assisted thymectomy in terms of the outcomes, although the robotic method may offer better flexibility and closer views during hard-to-reach procedures.

These methods that are less invasive have, over time, improved thymectomy by speeding up recovery and decreasing trauma from surgery, especially in patients with early-stage thymoma and MG without thymoma. These are often the preferred methods now in many places for their ability to lessen complications while still effectively treating the diseases. However, factors specific to patients, such as the size of the tumor, anatomical challenges, and surgeon expertise, continue to influence the choice of surgical method.

Consequently, the ongoing evolution of thymectomy methods highlights the importance of having a surgery plan that is tailored to the individual patient, to improve the success in treating diseases related to the thymus gland.