Anterior Mediastinal Mass

What is Anterior Mediastinal Mass?

The mediastinum is an area found between the lungs, which holds essential body parts such as the thymus, heart, major blood vessels, lymph nodes, nerves, and some parts of the esophagus and windpipe. It is surrounded by the sternum at the front, the thoracic vertebrae at the back, the thoracic inlet at the top, and the diaphragm at the bottom. The sides are defined by the protective membranes around the heart and mediastinum. This area includes important chest organs and structures. About 3% of all tumors that develop in the chest cavity are found in the mediastinum.

The mediastinum is divided into the front, middle, and back sections. Tumors in these areas vary greatly, with half of them appearing at the front. The most common tumors in the front of the mediastinum are known as the 4T’s – thymoma, teratoma, thyroid tissue, and severe – ‘terrible’ – lymphoma. These tumors pose unique challenges because they are so close to vital chest structures. Though image technology helps identify them, an accurate diagnosis often needs a combination of radiology, histology, and molecular techniques. The plan for treatment takes into account the details of the tumor, patient conditions, and tumor behavior. This article gives a comprehensive overview of clinical symptoms, diagnostic measures, and treatment options for tumors in the front of the mediastinum, also discussing recent developments and differing opinions on the subject.

What Causes Anterior Mediastinal Mass?

The anterior mediastinum, the area in front of the heart, goes through significant changes from childhood to adulthood. In kids, it’s home to the thymus, a crucial organ for the immune system, but as we get older, the thymus gets smaller and changes into a smaller area. This process leaves behind a section that is liable to develop tumors.

On top of housing the thymus, the anterior mediastinum also contains fat and lymph nodes. These correspond to the most common types of associated primary tumors. Although most mediastinal masses are not harmful, about 59% of them in the anterior compartment can be cancerous, and mainly comprise epithelial tumors.

Thymoma, making up less than 1% of adult cancers, is the most common kind of mass found in the anterior mediastinum in adults. Harmless masses of thymic origin are uncommon but include thymolipomas, which are composed of fat, and thymic cysts. Thymic cysts might be congenital, or they could be acquired, appearing as a result of an inflammatory tumor like Hodgkin lymphoma. It’s important to distinguish all these cases from thymic hyperplasia, where the thymus is enlarged but retains its original shape. Hyperplasia is often related to stress factors like chemotherapy or corticosteroid usage.

Germ cell tumors (GCTs) are another type of tumor characterized by primitive germ cells that fail to fully migrate during embryonic development. While they usually originate in the gonads, they make up 15% of anterior mediastinal masses. The most common type of GCT is the benign teratoma, which comprises tissues from at least two germ layers.

Primary mediastinal lymphomas make up approximately 10% of all mediastinal lymphomas. Hodgkin lymphoma accounts for 50% to 70% of primary lymphomas, with several types including the most common, nodular sclerosing. Non-Hodgkin lymphoma makes up around 15% to 25% of primary lymphomas.

Lastly, enlarged thyroid glands, also known as goiters, can occasionally show up as masses in the anterior mediastinum. Mediastinal goiters often arise from lower cervical thyroid lobes growing into the thoracic inlet, but in some cases, can stem from remnants of embryonic tissues. Less common causes of masses in the anterior mediastinum include parathyroid adenomas, hemangiomas, and sarcomas.

Risk Factors and Frequency for Anterior Mediastinal Mass

The main causes of lumps in the area between the lungs (anterior mediastinal masses) include:

• Thymic malignancies, or cancers in the thymus, which account for about 35% of cases,
• Lymphoma, or cancer in the lymphatic system, which accounts for about 25% of cases,
• Thyroid and other endocrine tumors, which are less common and make up 15% of cases,
• Benign teratoma, a non-cancerous tumor, and malignant GCTs, both responsible for about 10% of cases each,
• Benign thymic lesions, or benign tumors on the thymus, which represent 5% of cases.

The type of mass often depends on the patient’s age and sex. In men and women over 40, these lumps in the chest are usually due to thyroid goiter and thymic malignancies. About 30% to 50% of patients with thymomas also have paraneoplastic syndrome, a condition that arises from cancer but is not due to the local presence of cancer cells. This is often signified by MG, with 30-50% of thymoma patients developing MG. Other autoimmune disorders can also occur with thymomas.

For girls and women aged 10 to 39, the most common causes of these masses are lymphomas. The incidence of HL has two peak periods: in young adulthood and after the age of 50. Another common cause in this age group is thymic malignancies, mainly in women older than 20, and benign teratomas, primarily in women younger than 25.

In contrast, for boys and men aged 10 to 39, and children younger than 10, there isn’t one particular type of tumor that stands out as the most common. The type of tumor diagnosed often depends on how quickly symptoms appear. Symptoms that come on quickly are often a sign of LB-NHL, while an intermediate onset of symptoms may indicate HL or PMBCL. The onset of symptoms over a longer period might hint towards other tumor types like teratoma.

Signs and Symptoms of Anterior Mediastinal Mass

When doctors are evaluating anterior mediastinal masses or masses in the chest area, they conduct a thorough patient history and physical examination. Important factors such as age, gender, and rate of symptom development can help discern the type of mass. Sometimes, these masses are associated with abnormalities in other parts of the body.

Interestingly, an anterior mediastinal mass may be found by accident in patients with no symptoms, though about 60% of patients do have symptoms. Symptoms might include:

• Cough
• Chest pain
• Shortness of breath
• Changes in voice
• Coughing up blood
• Difficulty swallowing
• Fever, night sweats, or unintended weight loss
• Symptoms associated with a paraneoplastic syndrome like drooping eyelids, abdominal pain, confusion, and fatigue

The speed at which symptoms develop can be a clue about the type of tumor. Rapidly developing symptoms might indicate an aggressive tumor like lymphoma or germ cell tumors, while slower-onset symptoms might point towards less aggressive tumors like thymomas or teratomas. Doctors will also want to know about any other medical conditions, current medications, allergies to medications or contrast agents, family history of cancer, autoimmune diseases, or genetic syndromes, and any exposure to toxins, radiation, or chemicals.

The physical examination comprises several steps and helps the doctors gather more information. They begin by checking vital signs and looking for any signs of distress or disease in the patient. This might take the form of weight loss, paleness, or lymph nodes that are larger than normal, all of which could suggest disease. The doctor will also assess for signs of metastatic spread or lymphoma, check the eyes, face, and neck for signs of superior vena cava syndrome, and listen to the lungs and heart for abnormal sounds. Lastly, the doctor will check the abdominal area for enlarged organs or masses and assess cranial nerves for signs of Horner syndrome or other neurological deficits. Peripheral edema, dermatological conditions, and cutaneous manifestations of systemic diseases are also part of the examination. Gynecomastia in men and a scrotal examination can indicate specific types of mediastinal tumors.

Testing for Anterior Mediastinal Mass

To accurately diagnose anterior mediastinal masses, which are growths in the area between the lungs, doctors run a series of laboratory tests that provide necessary information about the cause of the mass and help shape the treatment approach. These laboratory tests can uncover crucial information, even if they do not definitively diagnose the condition.

Among the blood tests done are a complete blood count which could reveal abnormalities such as anemia, or conditions like leukocytosis or leukopenia that hint at problems with the blood system or systemic inflammation. A comprehensive metabolic panel can identify problems like electrolyte imbalances or liver or kidney dysfunction. Also done are tests for specific tumor markers along with inflammatory markers, and autoimmune markers if there is reason to suspect an underlying autoimmune disorder. Tests for infectious diseases such as Epstein-Barr virus, HIV, and tuberculosis may also be undertaken, especially in cases identified by systemic symptoms.

Once the results of blood work are available, medical imaging studies are carried out. These are critical to diagnosing anterior mediastinal masses, as they offer detail about the mass and where it is in the chest. These could be done through X-rays, CT scans, MRI, PET scans, and ultrasound. Each of these tests offers unique perspectives of the mass, helping doctors make a definitive diagnosis.

Moreover, tissue studies play a defining role in diagnosing anterior mediastinal masses. Biopsies provide an opportunity to study the mass directly and offer the clearest insights into its nature. However, not all masses require a biopsy for a diagnosis; conditions like thymoma, teratoma, and thyroid goiter can often be diagnosed without one.

The biopsy is followed by a histopathological examination of the tissue sample gathered during the biopsy process. This can help observe crucial microscopic elements of the biopsy samples, aiding doctors in making a diagnosis. In some cases, additional molecular testing is required to identify specific genetic or molecular traits that can be linked with various types of tumors. Molecular testing can provide valuable data on tumor behavior and also guide the best treatment approach.

In conclusion, diagnosing anterior mediastinal masses involves an intricate process of lab tests, imaging studies, and tissue studies. All these investigations when combined, give a comprehensive understanding of the disease, which in turn helps doctors decide the best treatment approach for the patient.

Treatment Options for Anterior Mediastinal Mass

The treatment of anterior mediastinal masses (a lump in the middle of the chest) depends on many factors like the cause, size, location, and the patient’s overall health. This includes conditions such as thymoma, germ cell tumors (GCTs), lymphoma, and substernal goiter.

Thymoma, a type of tumor in the thymus, is usually treated with surgery to remove the thymus and any affected areas around it. This treatment is often enough to cure it, especially in its early stages. However, in advanced cases, additional procedures like radiation therapy or chemotherapy may be required. If the thymoma can’t be removed through surgery, chemotherapy can help improve survival rates. Regular follow-ups with imaging studies are important to keep track of any changes or signs of recurrence.

Germ cell tumors, which can also develop in the center of the chest, are typically treated with a combination of surgery, chemotherapy, and sometimes radiation therapy. Depending on the extent of the disease, treatments may vary. Surgery, for example, is the first step and aims to remove the entire tumor. Chemotherapy is often used before and after surgery to shrink the tumor and eliminate any possible spread. Radiation therapy may also be considered, especially for untreatable or remaining disease cases.

Lymphoma, a type of cancer in the lymphatic system, is treated with a combination of chemotherapy, radiation therapy, and sometimes targeted therapy or immunotherapy. The specific mix of treatments depends on the subtype of lymphoma, its stage, patient’s age, and overall health. For Hodgkin Lymphoma (HL), the standard treatment is chemotherapy with a regimen of drugs called ABVD. In case it relapses, therapies targeting specific cellular functions or stem cell transplantation can be considered. In Non-Hodgkin Lymphoma (NHL), chemotherapy is based on the lymphoma subtype. Radiation therapy, targeted therapy, immunotherapy, and stem cell transplantation may be used as additional treatments.

Substernal goiter refers to an enlarged thyroid that extends down into the chest. In most cases, this condition requires surgery for removal, with the help of imaging studies to plan the surgery. After a complete thyroid removal, patients may need to take thyroid hormone replacement therapy. Regular follow-ups are necessary to monitor for any complications or recurrence.

In all these cases, treatment should ideally involve a team of doctors from different specialities working together to provide the best care for the patient.

What else can Anterior Mediastinal Mass be?

The front part of the area between the lungs, known as the anterior mediastinum, can have masses or lumps with a bunch of possible causes. These can be linked to various structures and tissues that exist within this region of the body. Besides the ones already mentioned, the common possible reasons for these lumps include:

• Swollen lymph nodes
• Cysts in the bronchi, the large passageways that carry air from the mouth to the lungs
• Cysts on the pericardium, the thin sac that surrounds the heart
• Enteric cysts, which are rarely found in the chest
• Ballooning (aneurysm) of the thoracic aorta, a large blood vessel in the chest
• Tumors in the esophagus, the tube that carries food from the mouth to the stomach
• Lymphangioma, a rare, non-cancerous mass in the lymphatic system
• Neurogenic tumors, which are usually benign and originate from nerve tissue
• Meningocele, a type of spina bifida where the protective layers around the spinal cord push out through the spinal opening
• Lesions in the thoracic spine
• Cancer that has spread from other parts of the body
• Infections, such as tuberculosis or fungal infections
• Inflammatory conditions, like sarcoidosis
• Parathyroid adenoma, a non-cancerous tumor of the parathyroid glands

Because of the many potential causes, it’s important to use thorough methods—like a combination of exams, scans, and tissue testing—to accurately diagnose and properly treat a mass in the anterior mediastinum.

What to expect with Anterior Mediastinal Mass

The outcome for patients with anterior mediastinal masses largely depends on several factors such as the type of disease, its stage, how effectively the treatment works, and the individual patient characteristics. Here’s a simplified explanation of the prognosis for some common anterior mediastinal masses:

Thymoma

In thymomas, the chances of recovery mainly depend on whether the entire tumor can be surgically removed. The Masaoka-Koga staging system helps estimate survival rates over a 5-year term. The rate is the highest for early-stage tumors and can be between 96% to 100%. On the other hand, metastatic disease (spreading to other parts of the body) has a poorer prognosis, with a 5-year survival rate between 11% to 50%. Large tumor sizes, young age, symptoms of airway or blood vessel compression, and specific tumor types can also worsen the prognosis.

Unlike thymomas, thymic carcinoma, and carcinoid tumors have a much lower survival rate. The Masaoka-Koga system is less useful in these cases. If the cells appear abnormal under the microscope, if there is tissue death within the tumor, or if the cells are dividing rapidly, these symptoms tend to indicate a worse prognosis.

Germ Cell Tumors

In germ cell tumors, teratomas have the best outlook since they are often benign. Seminomas and non-seminomas are serious conditions and their 5-year survival rates are 86% and 48% respectively. High levels of specific markers in the blood after chemotherapy often indicate a less favorable outcome.

Lymphoma

Lymphoma patients with stage I or II have a promising prognosis, with more than 90% cure rates using standard treatment. Stages IIIA and IIIB have cure rates between 60% to 70%, while stage IV disease has a poorer prognosis with a cure rate of 50% to 60%. Certain factors at the time of diagnosis can worsen the prognosis, such as being male, being older than 45, having low levels of albumin and hemoglobin in the blood, or having a high white blood cell count, and a low lymphocyte count.

Other Masses

The prognosis for other anterior mediastinal masses, such as substernal goiters or neurogenic tumors, can depend on the size of the tumor, how invasive it is, and the type of cells it contains. In general, benign masses usually have a better prognosis than malignant tumors, especially if they can be completely removed without causing other complications.

Possible Complications When Diagnosed with Anterior Mediastinal Mass

Anterior mediastinal masses, which are growths in the area between the lungs, can cause different complications based on their size, location, and whether they spread to surrounding structures. Here are some complications that can occur:

• Compression of nearby structures: These masses can press against nearby structures such as the airways, food pipe, and major blood vessels, leading to symptoms like shortness of breath, cough, difficulty swallowing, and swelling of the face and upper limbs.
• Respiratory distress due to airway obstruction: Blockage of airways by the mass can lead to difficulty in breathing and even life-threatening respiratory failure. In extreme cases, emergency procedures like airway stenting or surgery to remove the pressure may be required. It can also lead to fluid buildup or air leakage in the chest cavity, adding to the breathing difficulty.
• Cardiovascular complications: The mass can press against the heart or major blood vessels, interfering with blood flow and causing symptoms like facial swelling, neck vein distention, and in severe cases, critical conditions where the heart cannot pump enough blood. Heart rhythm disturbances or unstable blood pressure can also occur. Invasion of the heart cavity can lead to fluid build-up around the heart.
• Neurological complications: If the mass compresses or invades nerve structures, this can lead to nerve-related symptoms like droopy eyelids, decreased sweating, and changes in sensation or movement of the upper limbs.
• Malignant transformation and metastasis: Some of these masses, like thymomas or GCTs, can turn cancerous and spread to other parts of the body, forming tumors there and making treatment more complex.
• Endocrine dysfunction: These masses, particularly if they originate from the thymus or thyroid gland, can interfere with normal hormone activity and cause conditions like hyperthyroidism or hypothyroidism. Treatment would then involve hormone replacement therapy or other interventions.

It’s important to recognize and manage these complications promptly to prevent harm and improve the patient’s health outcomes. Careful management often involves a team of different specialists including thoracic surgeons, cancer specialists, and interventional radiologists.

Preventing Anterior Mediastinal Mass

People who have been diagnosed with anterior mediastinal masses need to thoroughly understand their specific disease, the treatment options available to them, and what they can expect moving forward. Equipped with this knowledge, patients can play an active role in deciding their course of treatment. It’s crucial for patients to regularly attend follow-up appointments, as it allows doctors to track their response to treatment and quickly identify any signs of the disease returning. Involving patients in their own healthcare process can help them understand their condition better, inspire them to stick to their treatment plans, and ultimately lead to the best possible health outcomes.