Mediastinal Seminoma

Mediastinal seminomas are a very rare germ cell tumor that occurs in the mediastinum. Germ cell tumors rarely occur outside of the gonads, with a rate of only 5% to 7%. If there is no primary testicular or ovarian mass, the tumor is considered extragonadal. The mediastinum and retroperitoneum are the most common locations for occurrence outside of the usual gonadal location, with the mediastinum being the most common extragonadal location. The seminomas can also occur in the sacrococcygeal region and central nervous system in the pineal gland. This occurs more commonly in children. Germ cell tumors comprise only 1% to 4% of all tumors found in the mediastinum and can be benign or malignant, with mediastinal seminomas being the latter. Mediastinal seminomas often have a very slow growth pattern, have limited potential to metastasize, symptoms are not very characteristic, and many patients often are asymptomatic with incidental findings. Mediastinal seminomas were first discovered in the late 1950s, and great progress has been made in curing patients of this disease and prolonging life. The 5-year survival rate has increased to 87% to 100%, similar to the results of testicular seminomas. Mediastinal seminomas are very sensitive to chemotherapy and radiation; therefore, these two modes are often the first line of treatment. Surgical intervention may also be used in the treatment of mediastinal seminomas. Mediastinal seminomas are usually found in the anterior-superior mediastinum. More specifically, they tend to develop where the innominate vein meets the superior vena cava. The mediastinum is defined by specific borders. The left and right pleura make up the lateral aspects of the mediastinum, while the thoracic inlet and the diaphragm make up the superior and inferior aspects, respectively. The anterior vertebral column is the posterior aspect of the mediastinum, while the anterior aspect is made up of the posterior sternum and costal cartilages. The mediastinum can then be subdivided into compartments, which aid in surgical planning. Mediastinal seminomas have the ability to become very large and can be difficult to differentiate from thymic fat and pericardial tissue. These tumors infiltrate surrounding organs early on in their growth process and, once they grow large enough, can cause the patient cardiac and respiratory problems, including difficulty breathing. If the tumor has spread outside of the thoracic cavity, it was probably found at a later stage. Metastasis occurs through the blood and mainly affects the lungs, liver, and bones. However, mediastinal seminomas usually remain contained in the chest.