title: Enthesopathy of the pectoralis major tendon mimicking osteoid osteoma. A case report with an unfortunate series of events.
abstract: BACKGROUND
  we present the case of an enthesopathy at the proximal humerus which was initially - due to the clinical history and a positive bone scintigraphy - regarded suspicious for metastatic breast cancer in a 50-year-old woman.
  
  
  METHODS
  after complementing radiographs and a magnetic resonance (MR) examination exhibiting a focally contrast enhancing juxtacortical osteolysis of the humerus, a metastasis seemed radiologically unlikely, but besides a traction-related periosteal reaction of the pectoralis major tendon an unusual osteoid osteoma could not unequivocally be ruled out. Although radiological follow-up was recommended the patient insisted on a surgical resection that was performed subsequently and confirmed an enthesopathy. Shortly after, she fractured her upper arm following minor trauma but is doing well after conservative treatment since then.
  
  
  CONCLUSIONS
  enthesopathies presenting as unusual periosteal reactions can mimic primary and secondary bone tumors and should always be included in the differential diagnosis.
authors.affiliation: Bone Tumor Reference Center at the Institute of Pathology University Hospital Basel, Switzerland.
authors.forename: Daniel
authors.initials: D
authors.lastname: Baumhoer
authors.affiliation: Bone Tumor Reference Center at the Institute of Pathology University Hospital Basel, Switzerland.
authors.forename: Gernot
authors.initials: G
authors.lastname: Jundt
authors.affiliation: Orthopaedic Department Basel University Childrens Hospital (UKBB), Switzerland.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Lenze
authors.affiliation: Department of Radiology and Nuclear Medicine, University of Basel Hospital, Switzerland.
authors.forename: Clemens
authors.initials: C
authors.lastname: Reisinger
authors.affiliation: Department of Radiology and Nuclear Medicine, University of Basel Hospital, Switzerland.
authors.forename: Anna
authors.initials: A
authors.lastname: Hirschmann
keywords: bone scan; enthesopathy; metastases; osteoid osteoma; pectoralis major tendon; secondary fracture