The mediastinum, located within the chest between the lungs and behind the breast bone, contains the heart, some large blood vessels, the esophagus, the trachea, the thymus and lymph nodes. It is divided into anterior, medial, and posterior compartments. Thymomas account for 20% of mediastinal tumors in adults making them the most common.1 Thymomas have been associated with myasthenia gravis, benign cytopenia, overt malignancy, hypogammaglobulinemia, and polymyositis.1 Myasthenia gravis in an autoimmune disease and in 75% of cases, the diagnosis includes thymic abnormalities. Due to these abnormalities these patients have an increased chance for thymomas.1 Also, due to invasion found in advanced cases, it is not rare to see superior vena cava syndrome as a presenting symptom.1 Although thymomas are the most common mediastinal cancer, Mediastinal Large B-Cell Lymphoma (MLBCL) begins as a growth in the mediastinum. MLBCL typically occurs in those ages 25-40 and is more common in women than in men.2 MLBCL is a form of Non-Hodgkin’s Lymphoma. Malignant Mediastinal Germ Cell tumors also occur in this area and it’s more common in males between ages 15-40 years old.2 These can be either pure seminomas or seminomatous carcinoma.2
Etiology:
Kevin Tsai
Thymoma etiology – 33% to 50% are associated with myasthenia gravis, 5% with red cell aglasia, and 5% with hypogammaglobulinemia3
Malignant mediastinal germ cell tumors are more common in males
Pure seminomas are most common with 3rd decade of life, followed by the 4th and 2nd decades
Nonseminomatous germ cell tumors occur in young adults (15 to 35 years)
Signs & Symptoms:
Erin Many tumors in the mediastinum initially present as asymptomatic.1 Often, tumors are accidentally found on routine chest x-rays. Symptoms that may be presented include:
Chest pain
Dyspnea (difficulty breathing)
Hoarseness
Superior vena cava syndrome
Dysphagia (difficulty swallowing)
Fever
Weight loss
Anorexia
Pain radiating to the neck and arms and substernal pressure
Gynecomastia (growth of male breasts seen in patients with choriocarcinoma)
Diagnostic Procedures:
Spencer Some of the various tests and diagnostic procedures for mediastinal tumors include:
Chest X-Ray
Computed Tomography (CT) Scan
Magnetic Resonance Imaging (MRI)
Mediastinoscopy - This diagnostic procedure is done in addition to a biopsy in which the patient is put under general anesthesia, and a small lighted tube is inserted into a minor incision in the patients chest.4 This method allows physicians to accurately diagnose 80-90% of mediastinal tumors and 95-100% of anterior mediastinal tumors.4
Histology:
Pablo Thymomas: are the main tumors originating in the mediastinum. These tumors originate in the epithelial cells of the thymus. Thymomas are associated with a condition called myasthenia gravis, which is a neuromuscular disorder. The three types of thymomas, lyphocytic, epithelial, and mixed epithelial.1
Type A, if the epithelial cells have an oval or fusiform shape.
Type B, if they have an epithelioid shape (Type B has three subtypes: B1 (lymphocyte-rich), B2 (cortical) and B3 (epithelial).
Type AB, if the tumor contains a combination of both cell types.5
Germ cell tumors: These tumors are what is called pure seminomas and occur in older adults. Nonseminomatous germ cell tumors (NSGCTs) also originate in the mediastinum and usually occur in the earlier decades of life.1 Thracheal Tumors: are squamous cell tumors in nature. As the name implies they affect the trachea.1
Lymph node drainage:
Becky
Mediastinal nodes: ¨ Superior mediastinal ¨ Tracheal ¨ Aortic ¨ Carinal and subcarinal ¨ Pulmonary ligaments
Intrapulmonic (hilar, bronchopulmonic) nodes:6
Mainstem bronchus
Interlobar
Lobar
Metastatic spread:
Adam Metastatic spread is rare for thymomas, but when it does occur, metastases to the liver, lung, and bone have been observed.3 For maglignant mediastinal germ cell tumors, the middle and posterior mediastinal lymph nodes along with the retroperitoneal nodes are usually involved.3
Grading:
Megan Tumor of the mediastinum are graded based on their growth process. They’re labeled indolent, or low grade, and aggressive, high grade. Indolent usually means slow growing and aggressive typically grows more quickly.2 MLBCL is known as an aggressive lymphoma and usually needs chemotherapy immediately.2
Staging:
Kevin Tsai
Two categories: invasive and noninvasive3
Staging of thymomas is based on degree of invasiveness
The pathologic staging system of Masaola is the most widely used
Stage I: Completely encapsulated microscopically & no microscopic encapsulation
Stage II: 1. Microscopic invasion into surrounding fatty tissue or pleura 2. Microscopic invasion into capsule
Stage III: Microscopic invasion into adjacent organs
Stage IV: A. Pleural or pericardial implants B. Lymphatogenous/hematogenous metastasis
Radiation side effects:
Erin Patients may experience short term and/or long term side effects.2 Short term side effects:
Mild skin reactions
Fatique
Esophagitis
Dysphagia (difficulty swallowing)
Cough
Long term side effects:
Radiation pneumonitis
Cardiac toxicity
Pericarditis1
Myelopathy
However, many late or long term side effects may not be seen due to the high local and systemic failure rate.1
Prognosis:
Spencer There are many different factors that determine a patient’s prognosis.
One of the more important factors associated with mediastinal cancer is how invasive the tumor is.3
Patients that undergo radical surgery to remove the tumor are far more likely to have better survival than those who have had a subtotal resection or biopsy.3
Depending on the specific type of cancer that is within the mediastinum, the histology can also play an important role as to having an overall better prognosis.3
Treatments:
Pablo Treatment of tumors affecting the mediastinum include the following.1
Thymomas: surgery radiation therapy and chemotherapy in some cases
Mediastinal germ cell tumors: thoracotomy, radiation therapy and chemotherapy
Nonseminomatous germ cell tumors (NSGCTs): Surgery, radiation therapy. These tumors do not respond well to chemotherapy
Thracheal tumors: Surgety, postoperative radiation therapy or brachytherapy and chemotherapy in conjunction with other modalities
TD 5/5:
Becky
Esophagus—6000cGy(ulceration, stricture)
Heart—4500cGy( pericarditis, pancarditis)
Lung—3000cGy( pneumonitis)
Spinal Cord—4500cGy( infarction, necrosis)
References:
Adam
Chao KS, Perez CA, Brady LW. Radiation Oncology Management Decisions. 2nd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2002.
Stinson D, Wallner PE. Respiratory system. In: Washington CM, Leaver D, eds. Principles and Practice of Radiation Therapy. 3rd ed. St. Louis, MO: Mosby-Elsevier; 2010: 666-691.
The mediastinum, located within the chest between the lungs and behind the breast bone, contains the heart, some large blood vessels, the esophagus, the trachea, the thymus and lymph nodes. It is divided into anterior, medial, and posterior compartments. Thymomas account for 20% of mediastinal tumors in adults making them the most common.1 Thymomas have been associated with myasthenia gravis, benign cytopenia, overt malignancy, hypogammaglobulinemia, and polymyositis.1 Myasthenia gravis in an autoimmune disease and in 75% of cases, the diagnosis includes thymic abnormalities. Due to these abnormalities these patients have an increased chance for thymomas.1 Also, due to invasion found in advanced cases, it is not rare to see superior vena cava syndrome as a presenting symptom.1 Although thymomas are the most common mediastinal cancer, Mediastinal Large B-Cell Lymphoma (MLBCL) begins as a growth in the mediastinum. MLBCL typically occurs in those ages 25-40 and is more common in women than in men.2 MLBCL is a form of Non-Hodgkin’s Lymphoma. Malignant Mediastinal Germ Cell tumors also occur in this area and it’s more common in males between ages 15-40 years old.2 These can be either pure seminomas or seminomatous carcinoma.2
Many tumors in the mediastinum initially present as asymptomatic.1 Often, tumors are accidentally found on routine chest x-rays.
Symptoms that may be presented include:
Some of the various tests and diagnostic procedures for mediastinal tumors include:
Thymomas: are the main tumors originating in the mediastinum. These tumors originate in the epithelial cells of the thymus. Thymomas are associated with a condition called myasthenia gravis, which is a neuromuscular disorder. The three types of thymomas, lyphocytic, epithelial, and mixed epithelial.1
- Type A, if the epithelial cells have an oval or fusiform shape.
- Type B, if they have an epithelioid shape (Type B has three subtypes: B1 (lymphocyte-rich), B2 (cortical) and B3 (epithelial).
- Type AB, if the tumor contains a combination of both cell types.5
Germ cell tumors: These tumors are what is called pure seminomas and occur in older adults. Nonseminomatous germ cell tumors (NSGCTs) also originate in the mediastinum and usually occur in the earlier decades of life.1Thracheal Tumors: are squamous cell tumors in nature. As the name implies they affect the trachea.1
Mediastinal nodes:
¨ Superior mediastinal
¨ Tracheal
¨ Aortic
¨ Carinal and subcarinal
¨ Pulmonary ligaments
Intrapulmonic (hilar, bronchopulmonic) nodes:6
Metastatic spread is rare for thymomas, but when it does occur, metastases to the liver, lung, and bone have been observed.3 For maglignant mediastinal germ cell tumors, the middle and posterior mediastinal lymph nodes along with the retroperitoneal nodes are usually involved.3
Tumor of the mediastinum are graded based on their growth process. They’re labeled indolent, or low grade, and aggressive, high grade. Indolent usually means slow growing and aggressive typically grows more quickly.2 MLBCL is known as an aggressive lymphoma and usually needs chemotherapy immediately.2
Patients may experience short term and/or long term side effects.2
Short term side effects:
Long term side effects:
However, many late or long term side effects may not be seen due to the high local and systemic failure rate.1
There are many different factors that determine a patient’s prognosis.
Treatment of tumors affecting the mediastinum include the following.1