title: Malignant mesenchymoma.
abstract: BACKGROUND
  Malignant mesenchymomas are rare soft tissue tumors that contain two or more distinct histologic subtypes of sarcoma within the same tumor (exclusive of a fibrosarcomatous or hemangiopericytomatous component). They are generally considered high grade neoplasms and are associated with a poor prognosis, although experience with these tumors is limited.
  
  
  METHODS
  We report 8 patients seen at our center over the last 22 years and describe the clinical course of a patient with a malignant mesenchymoma arising in the retroperitoneum whose experience typifies the aggressive behavior of this tumor.
  
  
  RESULTS
  All eight patients had large, high grade tumors located in the retroperitoneum or thigh. Six of the 8 died of disease and 2 were alive with disease at a median of 30 months from diagnosis.
  
  
  CONCLUSIONS
  Malignant mesenchymoma represents a particularly aggressive form of soft tissue sarcoma. Our experience with this disease highlights the need for more effective treatment strategies for these patients.
authors.affiliation: Department of Surgery Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
authors.forename: M S
authors.initials: MS
authors.lastname: Brady
authors.forename: G
authors.initials: G
authors.lastname: Perino
authors.forename: G
authors.initials: G
authors.lastname: Tallini
authors.forename: P
authors.initials: P
authors.lastname: Russo
authors.forename: J M
authors.initials: JM
authors.lastname: Woodruff
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008637:Mesenchymoma / Q000401:mortality* / Q000473:pathology / Q000628:therapy; D008875:Middle Aged; D012186:Retroperitoneal Neoplasms / Q000401:mortality / Q000473:pathology / Q000628:therapy; D012983:Soft Tissue Neoplasms / Q000401:mortality* / Q000473:pathology / Q000628:therapy; D013848:Thigh