title: Low-grade myofibroblastic sarcoma of the distal femur.
abstract: BACKGROUND
  Low-grade myofibroblastic sarcoma (myofibrosarcoma) is described to be a distinct atypical myofibroblastic tumor often with fibromatosis-like features and predilection for head and neck. Low-grade myofibroblastic sarcoma of bone is extremely rare.
  
  
  METHODS
  A 50-year-old woman was admitted to our hospital because she had experienced right knee pain for 2 years. Plain radiography showed a honeycombed lesion on the right distal femur, and computed tomography showed a bone tumor with cortex destruction invading the soft tissue. A biopsy specimen from the intraosseous lesion showed a hypocellular area of spindle cell proliferation with dense collagen deposition, which is reminiscent of a histological feature of desmoplastic fibroma. However, histological examination of the extraosseous lesion indicated a slightly hypercellular area containing scattered spindle-shaped atypical cells with enlarged nuclei, suggestive of low-grade sarcoma. Spindle-shaped atypical cells were immunohistochemically positive for SMA. A final diagnosis of low-grade myofibroiblastic sarcoma of the bone was made from a surgically resected specimen.
  
  
  CONCLUSIONS
  The patient was alive and well with no evidence of disease at 15 months after the surgery without any additional therapy.
  
  
  CONCLUSIONS
  Extensive sampling of a tumor may be necessary to determine the true nature of the tumor and to make an accurate diagnosis.
authors.affiliation: Department of Human Pathology, Juntendo University, School of Medicine, Japan. Electronic address: tysaitou@juntendo.ac.jp.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Saito
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Mitomi
authors.forename: Aiko
authors.initials: A
authors.lastname: Kurisaki
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Torigoe
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Takagi
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Suehara
authors.forename: Taketo
authors.initials: T
authors.lastname: Okubo
authors.forename: Kazuo
authors.initials: K
authors.lastname: Kaneko
authors.forename: Takashi
authors.initials: T
authors.lastname: Yao