timoma

Thymoma is a tumor that arises from the thymic epithelial cells in the anterior mediastinum. It is usually slow growing and may be discovered incidentally or present with symptoms related to a mediastinal mass, such as cough or chest discomfort. A key feature of thymoma is its association with autoimmune conditions, most notably myasthenia gravis, but it can also occur with pure red cell aplasia and hypogammaglobulinemia. Thymomas are distinct from thymic carcinomas, which are more aggressive and less commonly associated with autoimmune disease.

Epidemiology and presentation commonly involve adults in mid to late life, though thymomas can occur at various ages. Many patients are asymptomatic at diagnosis. When present, symptoms reflect local mass effect or paraneoplastic phenomena, including neuromuscular symptoms from myasthenia gravis or constitutional symptoms in advanced disease.

Histology and classification follow the World Health Organization system, which groups thymomas into types A, AB, B1, B2, and B3, based on epithelial cell morphology and lymphocyte content. These types correlate with prognosis and behavior, with type A generally more indolent and higher-grade B types more likely to be associated with invasiveness. Thymic carcinomas, which are separate from thymomas, are typically more aggressive and have different histologic and clinical features.

Diagnosis typically involves imaging with CT or MRI of the chest to define the lesion and its extent. Surgical resection is the primary treatment for localized thymoma, often performed as an en bloc thymectomy. Adjuvant radiotherapy is considered for invasive or incompletely resected tumors. Chemotherapy, usually platinum-based, is used for advanced or unresectable disease. Prognosis depends on stage at diagnosis, completeness of resection, and histologic type; localized, completely resected thymomas have the best outcomes, while advanced disease carries a poorer prognosis.