title: Retroperitoneal smooth muscle tumor of uncertain malignant potential after hysterectomy: a case report.
abstract: BACKGROUND
  Smooth muscle tumors of uncertain malignant potential represent a histologically heterogeneous group of uterine smooth muscle tumors that cannot be diagnosed as either benign or malignant. Smooth muscle tumors of uncertain malignant potential are usually clinically benign, but should be considered tumors of low malignant potential because they can occasionally recur or metastasize to distant sites.
  
  
  METHODS
  We report the case of a 62-year-old Mongol woman diagnosed with a retroperitoneal smooth muscle tumor of uncertain malignant potential and lung metastasis, with a history of prior hysterectomy. The case was initially misdiagnosed as retroperitoneal sarcoma, and our patient received chemotherapy. However, no interval change in the size of the retroperitoneal mass and metastatic lung nodules was seen over a period of at least five years. She underwent partial resection of the retroperitoneal mass for the purposes of debulking and establishing a histopathological diagnosis. The diagnosis of the retroperitoneal mass was then confirmed as a smooth muscle tumor of uncertain malignant potential.
  
  
  CONCLUSIONS
  Smooth muscle tumors of uncertain malignant potential have an unpredictable clinical course, and relapses generally appear to occur after a long disease-free interval of up to several years. Therefore, patients diagnosed with smooth muscle tumors of uncertain malignant potential should receive long-term follow-up.
authors: Division of Medical Oncology, Department of Internal Medicine, Seoul St Mary's Hospital, Seoul, Korea. hgchun@catholic.ac.kr.
authors: Hye Sung
authors: HS
authors: Won
authors: Hoo Geun
authors: HG
authors: Chun
authors: Kyungji
authors: K
authors: Lee
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