title: Lipomatous hemangiopericytoma of the head and neck: immunohistochemical and DNA ploidy analyses.
abstract: BACKGROUND
  Lipomatous hemangiopericytoma (LHPC) is a newly described rare soft tissue tumor with unpredictable biologic behavior and is difficult to diagnose by conventional histologic parameters. The molecular analyses of this entity to date are sparse. Only a few cases of LHPC have been reported. Although one case of LHPC in the sinonasal region was briefly reported, this is the first case in the head and neck region with detailed clinicopathologic features and molecular analysis of this entity.
  
  
  METHODS
  We reported a case of LHPC in a 55-year-old woman with a slowly growing lesion in the occipital area that was diagnosed by CT and MRI and removed surgically. Immunohistochemical and DNA ploidy analyses were performed.
  
  
  RESULTS
  A panel of 16 markers was included for immunohistochemical analysis. Diffuse immunopositivity of CD57 in our case provides supportive evidence that LHPC is linked with HPC because this marker is also present in approximately 50% of conventional HPCs. CD57 should be used in the immunohistochemical panel in any lesion suspected to be LHPC. Furthermore, CD57 along with CD34 and XIIIa is thought to stain for primitive mesenchymal stem cells, suggesting a bimodal/multimodal differentiation of LHPC. By flow cytometry, we found that tumor cells were 100% diploid with the S-phase fraction (SPF) being 3.21%. A significant positive correlation was detected between nuclear proliferating index and SPF (p < 0.001, by Spearman analysis). These findings provide molecular evidence indicating a benign nature of LHPC.
  
  
  CONCLUSIONS
  Contrary to the old belief that HPC has an aggressive nature, this variant of tumor looks less aggressive. The patient was followed for 1 year without any evidence of recurrence, supporting our pathologic hypothesis.
authors.affiliation: Roswell Park Cancer Institute, State University of New York, Buffalo, New York 14263, USA.
authors.forename: Sadir J
authors.initials: SJ
authors.lastname: Alrawi
authors.forename: George
authors.initials: G
authors.lastname: Deeb
authors.forename: Richard
authors.initials: R
authors.lastname: Cheney
authors.forename: Paul
authors.initials: P
authors.lastname: Wallace
authors.forename: Thom
authors.initials: T
authors.lastname: Loree
authors.forename: Nestor
authors.initials: N
authors.lastname: Rigual
authors.forename: Wesley
authors.initials: W
authors.lastname: Hicks
authors.forename: Dongfeng
authors.initials: D
authors.lastname: Tan
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis; D018959:CD57 Antigens / Q000032:analysis; D004273:DNA, Neoplasm / Q000032:analysis; D005260:Female; D006393:Hemangiopericytoma / Q000235:genetics* / Q000473:pathology* / Q000601:surgery; D006801:Humans; D007150:Immunohistochemistry; D008067:Lipoma / Q000235:genetics* / Q000473:pathology* / Q000601:surgery; D008875:Middle Aged; D011003:Ploidies; D012983:Soft Tissue Neoplasms / Q000235:genetics* / Q000473:pathology* / Q000601:surgery
chemical_list: D014408:Biomarkers, Tumor; D018959:CD57 Antigens; D004273:DNA, Neoplasm