title: Mesenteric extraskeletal osteosarcoma with telangiectatic features: a case report.
abstract: BACKGROUND
  Extraskeletal osteosarcoma is a rare malignant mesenchymal tumor, with a predominant occurrence in the extremities. Only two cases of mesenteric extraskeletal osteosarcoma have been documented. We describe an unusual case of extraskeletal osteosarcoma with telangiectatic features occurring in the mesentery.
  
  
  METHODS
  A 67-year-old male presented with blood-tinged stool of 1-month's duration. On colonoscopy, a solid mass was detected protruding from the colon wall. Computed tomography showed a 15 x 9.7 cm heterogeneously enhancing mass, with mottled calcification and a cystic portion, occupying the left upper quadrant of the abdominal cavity. Curative resection of the tumor was performed, and the excised tumor was composed of large multilocular cysts containing old hematomas and necrotic debris. The histology revealed an osteosarcoma showing osteoid formation and blood-filled spaces lined with atypical cells. Despite postoperative chemotherapy, he developed a recurrent peritoneal mass and multiple lung metastases 3 months postoperatively.
  
  
  CONCLUSIONS
  Given the rarity of cases of mesenteric extraskeletal osteosarcoma, its biologic behavior at this location remains to be determined. However, extraskeletal osteosarcoma with telangiectatic features is an uncommon entity to be recognized because of the possible fatal outcome related to the tumors.
authors.affiliation: Department of Pathology, Chonnam National University Medical School, Hak-dong, Dong-gu, Gwangju, Republic of Korea. azimmed@hanmail.net <azimmed@hanmail.net>
authors.forename: Kyung Hwa
authors.initials: KH
authors.lastname: Lee
authors.forename: Jae Kyoon
authors.initials: JK
authors.lastname: Joo
authors.forename: Dong Yi
authors.initials: DY
authors.lastname: Kim
authors.forename: Ji Shin
authors.initials: JS
authors.lastname: Lee
authors.forename: Chan
authors.initials: C
authors.lastname: Choi
authors.forename: Jae Hyuk
authors.initials: JH
authors.lastname: Lee
mesh_terms: D000368:Aged; D003110:Colonic Neoplasms / Q000150:complications / Q000175:diagnosis* / Q000601:surgery; D006801:Humans; D008297:Male; D008643:Mesentery / Q000473:pathology*; D012516:Osteosarcoma / Q000150:complications / Q000175:diagnosis* / Q000601:surgery; D013684:Telangiectasis / Q000150:complications / Q000175:diagnosis* / Q000601:surgery