title: Aggressive aneurysmal bone cyst in association with polyostotic fibrous dysplasia: A case report.
abstract: BACKGROUND
  Aneurysmal bone cyst occurring in the setting of previously diagnosed fibrous dysplasia is rare. While both are benign processes, pain, compression of nearby structures and risk of fracture can require treatment.
  
  
  METHODS
  In this report, we describe a 56 year old male who developed an aggressive aneurysmal bone cyst secondary to fibrous dysplasia in the proximal tibia over a period of 8 months. He required an above knee amputation for disease and symptom control due to the aggressive nature of disease and medical comorbidities.
  
  
  CONCLUSIONS
  The diagnosis of a secondary lesion can prove difficult. It is important to exclude a malignant disease process, particularly when imaging demonstrates an aggressive appearance. In this case, repeat imaging, CT guided biopsies and an open biopsy were performed to exclude malignancy prior to definitive surgical management.
  
  
  CONCLUSIONS
  In order to exclude secondary lesions, we suggest further investigation for new onset pain in the setting of a benign lesion.
authors.affiliation: Department of Orthopaedics, St Vincent's Hospital Melbourne, 41 Victoria Parade, Fitzroy, Victoria 3065 Australia; Bone and Soft Tissue Sarcoma Service, Peter MacCallum Cancer Institute, Melbourne, Victoria 3002, Australia. Electronic address: nathananderson9@gmail.com.
authors.forename: Nathan
authors.initials: N
authors.lastname: Anderson
authors.affiliation: Department of Orthopaedics, St Vincent's Hospital Melbourne, 41 Victoria Parade, Fitzroy, Victoria 3065 Australia; Bone and Soft Tissue Sarcoma Service, Peter MacCallum Cancer Institute, Melbourne, Victoria 3002, Australia; Department of Surgery, The University of Melbourne, Parkville, Victoria 3002, Australia. Electronic address: claudibella@hotmail.it.
authors.forename: Claudia
authors.initials: C
authors.lastname: DiBella
authors.affiliation: Department of Radiology, St Vincent's Hospital Melbourne, 41 Victoria Parade, Fitzroy, Victoria 3065, Australia. Electronic address: Marcus.Pianta@svhm.org.au.
authors.forename: Marcus
authors.initials: M
authors.lastname: Pianta
authors.affiliation: Department of Pathology, St Vincent's Hospital Melbourne, 41 Victoria Parade, Fitzroy, Victoria 3065, Australia. Electronic address: John.Slavin@svhm.org.au.
authors.forename: John
authors.initials: J
authors.lastname: Slavin
authors.affiliation: Department of Orthopaedics, St Vincent's Hospital Melbourne, 41 Victoria Parade, Fitzroy, Victoria 3065 Australia; Bone and Soft Tissue Sarcoma Service, Peter MacCallum Cancer Institute, Melbourne, Victoria 3002, Australia; Department of Surgery, The University of Melbourne, Parkville, Victoria 3002, Australia. Electronic address: sarcoma@bigpond.net.au.
authors.forename: Peter
authors.initials: P
authors.lastname: Choong
keywords: Aneurysmal bone cyst; Fibrous dysplasia