Mediastinum


 * **Epidemiolgy:** || Megan

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 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 || Mediastinal nodes: ¨ Superior mediastinal ¨ Tracheal ¨ Aortic ¨ Carinal and subcarinal ¨ Pulmonary ligaments
 * **Etiology:** || Kevin Tsai
 * Thymoma etiology – 33% to 50% are associated with myasthenia gravis, 5% with red cell aglasia, and 5% with hypogammaglobulinemia 3
 * 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
 * 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:** || <span style="color: #ff0000; font-family: Arial,Helvetica,sans-serif;">Spencer
 * <span style="color: #ff0000; font-family: Arial,Helvetica,sans-serif;">Chest X-Ray
 * <span style="color: #ff0000; font-family: Arial,Helvetica,sans-serif;">Computed Tomography (CT) Scan
 * <span style="color: #ff0000; font-family: Arial,Helvetica,sans-serif;">Magnetic Resonance Imaging (MRI)
 * <span style="color: #ff0000; font-family: Arial,Helvetica,sans-serif;">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. <span style="color: #ff0000; font-family: Arial,Helvetica,sans-serif; vertical-align: super;">4 <span style="color: #ff0000; font-family: Arial,Helvetica,sans-serif;"> This method allows physicians to accurately diagnose 80-90% of mediastinal tumors and 95-100% of anterior mediastinal tumors. <span style="color: #ff0000; font-family: Arial,Helvetica,sans-serif; vertical-align: super;">4 ||
 * **Histology:** || Pablo
 * 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
 * **Lymph node drainage:** || Becky

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 || <span style="color: #ff00ff; font-family: 'Times New Roman',Times,serif;">Patients may experience short term and/or long term side effects.2 <span style="color: #ff00ff; font-family: 'Times New Roman',Times,serif;">Short term side effects:
 * Mainstem bronchus
 * Interlobar
 * Lobar ||
 * **Metastatic spread:** || Adam
 * **Grading:** || Megan
 * **Staging:** || Kevin Tsai
 * Two categories: invasive and noninvasive 3
 * 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:** || <span style="color: #ff00ff; font-family: 'Times New Roman',Times,serif;">Erin
 * <span style="color: #ff00ff; font-family: 'Times New Roman',Times,serif;">Mild skin reactions
 * <span style="color: #ff00ff; font-family: 'Times New Roman',Times,serif;">Fatique
 * <span style="color: #ff00ff; font-family: 'Times New Roman',Times,serif;">Esophagitis
 * <span style="color: #ff00ff; font-family: 'Times New Roman',Times,serif;">Dysphagia (difficulty swallowing)
 * <span style="color: #ff00ff; font-family: 'Times New Roman',Times,serif;">Cough

<span style="color: #ff00ff; font-family: 'Times New Roman',Times,serif;">Long term side effects:
 * <span style="color: #ff00ff; font-family: 'Times New Roman',Times,serif;">Radiation pneumonitis
 * <span style="color: #ff00ff; font-family: 'Times New Roman',Times,serif;">Cardiac toxicity
 * <span style="color: #ff00ff; font-family: 'Times New Roman',Times,serif;">Pericarditis1
 * <span style="color: #ff00ff; font-family: 'Times New Roman',Times,serif;">Myelopathy

<span style="color: #ff00ff; font-family: 'Times New Roman',Times,serif;">However, many late or long term side effects may not be seen due to the high local and systemic failure rate.1 || <span style="color: #ff0000; font-family: Arial,Helvetica,sans-serif;">There are many different factors that determine a patient’s prognosis. Treatment of tumors affecting the mediastinum include the following. 1 Back to Week 3
 * **Prognosis:** || <span style="color: #ff0000; font-family: Arial,Helvetica,sans-serif;">Spencer
 * <span style="color: #ff0000; font-family: Arial,Helvetica,sans-serif;">One of the more important factors associated with mediastinal cancer is how invasive the tumor is. <span style="color: #ff0000; font-family: Arial,Helvetica,sans-serif; vertical-align: super;">3
 * <span style="color: #ff0000; font-family: Arial,Helvetica,sans-serif;">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. <span style="color: #ff0000; font-family: Arial,Helvetica,sans-serif; vertical-align: super;">3
 * <span style="color: #ff0000; font-family: Arial,Helvetica,sans-serif;">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. <span style="color: #ff0000; font-family: Arial,Helvetica,sans-serif; vertical-align: super;">3 ||
 * **Treatments:** || Pablo
 * 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
 * 1) Chao KS, Perez CA, Brady LW. Radiation Oncology Management Decisions. 2nd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2002.
 * 2) Mediastinal Large B-Cell Lymphoma (MLBCL). Macmillan Website.[|http://www.macmillan.org.uk/Cancerinformation/Cancertypes/Lymphomanon-Hodgkin/TypesofNHL/MediastinallargeB-cell.aspx#DynamicJumpMenuManager_6_Anchor_6]Updated January 2013. Accessed June 10, 2013.
 * 3) Chao KS, Perez CA, Brady LW. Radiation Oncology Management Decisions. 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2011.
 * 4) Mediastinum Disease and Conditions. Cleveland Clinic Web Site. http://my.clevelandclinic.org/disorders/mediastinal_tumor/hic_mediastinal_tumors.aspx. Accessed June 10, 2013.
 * 5) International Thymic Malignancy Interest Group. [|www.itmig.org/.../Strobel-et-al.-Molecular-Pathology-in-Thymoma-JTO]. Accessed Jun 8, 2013.
 * 6) 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. ||