[Rapid Growing Anterior Mediastinal Leiomyosarcoma with Pericardial Infiltration:Report of a Case].

Primary mediastinal leiomyosarcoma is extremely rare, and few reports in the literature have described the clinical features of this malignancy. We report a case of a small anterior mediastinal leiomyosarcoma that showed rapid growth within a short period. An 85-year-old woman showed a small anterior mediastinal tumor on chest computed tomography (CT), three months prior to presentation. Contrast-enhanced chest CT revealed rapid tumor growth, and positron emission tomography/CT revealed significant 18-fluorodeoxyglucose uptake, suggestive of malignancy. Thoracoscopic tumor resection was performed via the left thoracic approach. In addition to the tumor and surrounding anterior mediastinal tissue, we resected an area of pericardial infiltration. The tumor was diagnosed as a primary mediastinal leiomyosarcoma based on histopathological and immunohistochemical findings.