title: Liposarcoma masquerading as an inflammatory pseudotumor: a case report.
abstract: BACKGROUND
  Distinguishing an atypical lipomatous tumor/well-differentiated liposarcoma from a benign lipomatous tumor on morphology alone can be difficult and there is an established role for MDM2 fluorescent in situ hybridization studies in making this differential diagnosis. There is no literature on the role for MDM2 fluorescent in situ hybridization studies in distinguishing between a well-differentiated liposarcoma with extreme fibrosis and a fibrosing inflammatory pseudotumor.
  
  
  METHODS
  We report the case of a 76-year-old Australian woman initially diagnosed by an excision biopsy with a retroperitoneal fibrosing inflammatory pseudotumor. She was then diagnosed 5 years later with a pleomorphic undifferentiated sarcoma. Upon review of the original resection specimen, we were able to show that the tumor demonstrated MDM2 amplification. MDM2 amplification was also present in some adjacent bland adipose tissue, and also in the tumor recurrence as a pleomorphic undifferentiated sarcoma.
  
  
  CONCLUSIONS
  Taken together, our findings provide strong evidence that the original tumor was a misdiagnosed well-differentiated liposarcoma with extreme fibrosis, and the pleomorphic undifferentiated sarcoma represented a recurrence of the same tumor with dedifferentiation.
authors.affiliation: Department of Anatomical Pathology, Royal North Shore Hospital, Pacific Highway, St Leonards, NSW, 2065, Australia.
authors.forename: Jessica J H
authors.initials: JJ
authors.lastname: Reagh
authors.affiliation: Department of Anatomical Pathology, Royal North Shore Hospital, Pacific Highway, St Leonards, NSW, 2065, Australia.
authors.forename: Robert P
authors.initials: RP
authors.lastname: Eckstein
authors.affiliation: Tissue Pathology and Diagnostic Oncology, Royal Prince Alfred Hospital, Building 94 Missenden Road, Camperdown, NSW, 2050, Australia.
authors.forename: Christina I
authors.initials: CI
authors.lastname: Selinger
authors.affiliation: Department of Surgery, Royal North Shore Hospital, Pacific Highway, St Leonards, NSW, 2065, Australia.
authors.forename: Justin
authors.initials: J
authors.lastname: Evans
authors.affiliation: Tissue Pathology and Diagnostic Oncology, Royal Prince Alfred Hospital, Building 94 Missenden Road, Camperdown, NSW, 2050, Australia.
authors.forename: Sandra A
authors.initials: SA
authors.lastname: O'Toole
authors.affiliation: Department of Anatomical Pathology, Royal North Shore Hospital, Pacific Highway, St Leonards, NSW, 2065, Australia. affgill@med.usyd.edu.au.|University of Sydney, Sydney, NSW, 2006, Australia. affgill@med.usyd.edu.au.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Gill
mesh_terms: D000368:Aged; D014408:Biomarkers, Tumor; D003937:Diagnosis, Differential; D005260:Female; D005784:Gene Amplification; D006104:Granuloma, Plasma Cell / Q000175:diagnosis* / Q000235:genetics; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007249:Inflammation / Q000473:pathology*; D008080:Liposarcoma / Q000175:diagnosis*; D009364:Neoplasm Recurrence, Local; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics; D012185:Retroperitoneal Fibrosis / Q000175:diagnosis* / Q000235:genetics / Q000276:immunology; D012983:Soft Tissue Neoplasms / Q000175:diagnosis* / Q000235:genetics / Q000276:immunology
chemical_list: D014408:Biomarkers, Tumor; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2
keywords: Benign lipomatous tumor; Liposarcoma; MDM2