Thymomas Definition and Classification: Thymomas are rare tumors originating from the epithelial cells of the thymus gland, a vital organ involved in the development of T lymphocytes (T cells) and the immune system. Thymomas are classified based on their histological features and the extent of their invasion into surrounding tissues. The World Health Organization (WHO) classifies thymomas into several types, including:  Type A: Medullary thymoma with predominantly spindle-shaped epithelial cells.  Type AB: Mixed thymoma with a combination of medullary and cortical features.  Type B1: Thymoma with predominantly cortical-type epithelial cells and mild lymphocytic infiltration.  Type B2: Thymoma with more prominent cortical-type epithelial cells and moderate lymphocytic infiltration.  Type B3: Thymoma with a predominance of atypical epithelial cells and scant lymphocytic infiltration.  Type C: Thymic carcinoma, which is a more aggressive form of thymic epithelial tumor, showing high-grade malignancy. Epidemiology: Thymomas are relatively rare, with an incidence of approximately 1-2 cases per million people per year. They most commonly affect adults, with a peak incidence in the 40s to 60s age group. There is no strong gender predilection, though some studies suggest a slight male predominance. Thymomas can occur sporadically or in association with autoimmune diseases. Pathophysiology: Thymomas arise from the thymic epithelial cells and are often slow-growing tumors. They can cause local symptoms by compressing adjacent structures or invading surrounding tissues. The pathogenesis of thymomas is not fully understood, but they may be associated with genetic mutations and abnormalities affecting thymic epithelial cell function. Thymomas can be benign or malignant, with malignant forms often referred to as thymic carcinomas. Clinical Presentation: Thymomas often present with a range of symptoms depending on their size, location, and associated complications:  Asymptomatic Cases: Many thymomas are discovered incidentally during imaging studies for unrelated conditions.  Symptoms from Local Compression: Cough, chest pain, dyspnea (shortness of breath), or superior vena cava syndrome (SVC syndrome) due to compression of the major veins.  Autoimmune Disorders: Thymomas are associated with autoimmune conditions, such as myasthenia gravis (MG), in up to 30% of patients. Other autoimmune disorders like systemic lupus erythematosus (SLE) or rheumatoid arthritis can also be associated. Diagnosis: The diagnosis of thymomas involves:  Imaging: Chest X-ray or computed tomography (CT) scans can identify thymoma presence and assess its size and extent.  Biopsy: Tissue samples obtained through needle biopsy or surgical resection provide histological confirmation and classification of the tumor.  Immunohistochemistry: Helps differentiate thymomas from other types of tumors and determine the specific subtype. Treatment: Treatment of thymomas typically involves a multidisciplinary approach:  Surgery: The primary treatment for thymomas is surgical resection. Complete removal of the tumor is often curative, particularly for earlystage disease.  Radiation Therapy: May be used as adjuvant treatment following surgery or for patients who are not surgical candidates. It can also be used for local control in cases of residual disease or relapse.  Chemotherapy: For advanced or metastatic thymomas, chemotherapy may be employed, often in combination with radiation therapy. Prognosis: The prognosis of thymomas depends on factors such as tumor type, stage at diagnosis, and completeness of surgical resection. The overall 5-year survival rate for patients with thymomas is favorable, particularly for those with early-stage disease. Thymic carcinomas, being more aggressive, have a poorer prognosis compared to benign thymomas. Early detection and appropriate treatment are key to improving outcomes and managing the disease effectively.