A mediastinal tumor is an abnormal growth that develops in the area between the lungs, known as the mediastinum. There are several synonyms for mediastinal tumor, including mediastinal mass, chest tumor, and thymic neoplasm. A thymic neoplasm refers specifically to a tumor originating in the thymus gland. Other types of tumors that can occur in the mediastinum include lymphoma, germ cell tumors, and neurogenic tumors. Symptoms of a mediastinal tumor can include chest pain, shortness of breath, coughing, and difficulty swallowing. Treatment depends on the type and size of the tumor and may involve surgery, radiation therapy, and chemotherapy.