From the Guidelines
Thymoma is a rare tumor that originates from the epithelial cells of the thymus gland, which is located in the upper chest beneath the breastbone, and its treatment typically involves complete surgical resection, often followed by radiation therapy or chemotherapy depending on the stage and completeness of resection, as recommended by the most recent guidelines 1.
Definition and Characteristics
Thymoma is the most common tumor of the anterior mediastinum, accounting for about 20-30% of all mediastinal tumors. Thymomas grow slowly and often don't cause symptoms until they press on surrounding structures. When symptoms do occur, they may include:
- Chest pain
- Cough
- Difficulty breathing
- Superior vena cava syndrome About 30-50% of patients with thymoma also have myasthenia gravis, an autoimmune disorder causing muscle weakness, as noted in studies 1. Other autoimmune conditions like pure red cell aplasia and hypogammaglobulinemia can also be associated with thymoma.
Treatment and Prognosis
The prognosis for thymoma varies based on its invasiveness, with the World Health Organization classification system (types A, AB, B1, B2, B3, and thymic carcinoma) and the Masaoka staging system helping to determine treatment approaches and outcomes. Complete surgical resection of the entire thymus gland, including all mediastinal tissues, is recommended as the standard of care, as stated in the most recent guideline 1. Regular follow-up is essential as thymomas can recur even many years after initial treatment. Radiation therapy or chemotherapy may be used in addition to surgery, depending on the stage and completeness of resection, with guidelines recommending adjuvant therapy for incompletely resected thymomas 1.
From the Research
Definition and Overview of Thymoma
- Thymoma is a type of cancer that originates in the thymus, a small organ located in the chest, behind the sternum and between the lungs 2.
- Thymomas and thymic carcinomas are thymic epithelial tumors that constitute approximately 15% of all mediastinal masses 2.
- Thymoma is often associated with myasthenia gravis, an autoimmune disorder of the neuromuscular junction characterized by muscular fatigability 3.
Clinical Manifestations and Diagnosis
- From 28 to 66% of thymomas cause chest symptoms as the initial manifestation; the rest are discovered on routine chest roentgenograms or during investigations prompted by the presence of a paraneoplastic syndrome 2.
- Forty percent of patients with thymoma have one or more paraneoplastic syndromes, including myasthenia gravis, pure red cell aplasia, and hypogammaglobulinemia 2.
- Extrathymic malignant lesions develop in up to 20% of patients 2.
Treatment and Prognosis
- Traditional histologic classifications have not accurately predicted tumor behavior; a recently developed classification based on cellular differentiation toward thymic medullary or cortical epithelium may correlate better with prognosis 2.
- The prognosis is best predicted by stage of the tumor determined intraoperatively and is poorer in patients with incomplete resection than in those with complete resection of the thymoma 2.
- In addition to surgical intervention, irradiation and chemotherapy have important roles in the management of thymomas, particularly in advanced stages 2, 4.
- Chemotherapy regimens such as docetaxel plus cisplatin have shown therapeutic potential in patients with metastatic thymoma and myasthenia gravis 5.
- Combined-modality therapy with chemotherapy and radiation therapy has been shown to be feasible and associated with prolonged progressive-free survival in patients with unresectable thymoma 4.