• Thymic tumors occur in anterior mediastinum and include thymomas, lymphomas, Hodgkin lymphoma
• Most common type often difficult to distinguish from lymphoma
• 3 predominant cell types
• Neuromuscular disorder characterized by weakness and fatigability of voluntary muscles
• Decreased number of acetylcholine receptors at neuromuscular junctions
• Believed to be autoimmune process
• 30% of patients with thymoma have MG
• Thymoma develops in 15% of patients with MG
• Thymomas associated with paraneoplastic syndromes including:
• MG is more commonly associated with lymphocytic variety
• 50% of asymptomatic cases identified on chest film
• Chest pain dysphagia, MG, dyspnea, or superior vena cava syndrome most common if symptomatic
• Easy fatigability in patients with MG
• Chest film: Anterior mediastinal mass
• CT scan: Useful in assessing extent of lesion
• MRI: Can assess vascular invasion
•Myasthenia Gravis (MG): Decremental response in muscular contraction to repeated stimulation with improvement after edrophonium administration (short-acting anticholinesterase)
• Definitive diagnosis: Histologic tissue analysis
• Do not biopsy small, well-encapsulated mediastinal masses
• Complete excision, otherwise risk tumor seeding
• Thymic carcinoma
• Treatment of choice for thymoma is total thymectomy
• Performed via median sternotomy, trap door, or clamshell approach
• Cervical incision not useful for malignant disease, only for benign disease
• Stages I, II, III should be aggressively resected
• En bloc resection with associated structures is warranted if complete resection is possible
• Large (> 5 cm) neoadjuvant chemotherapy may shrink tumor
• Large lesions with gross invasion-biopsy to confirm histologic diagnosis, then neoadjuvant therapy prior to resection
• MG indication for early thymectomy
• Anticholinesterase drugs initial treatment and used aggressively in postoperative period
• Corticosteroids used in select cases
• Plasmapheresis can minimize need for anticholinesterase agents
• Avoid muscle relaxants and atropine
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