title: Microvascular proliferations in arteriovenous malformations relate to high-flow characteristics, inflammation, and previous therapeutic embolization of the lesion.
abstract: BACKGROUND
  Episodes of microvascular proliferation associated with volume expansion have been observed in arteriovenous malformations (AVMs) of skin and soft tissue.
  
  
  OBJECTIVE
  We sought to investigate the relationship between a microvascular proliferative response and flow velocity in AVMs.
  
  
  METHODS
  Resection specimens of 80 AVMs were clinically categorized as either high- or low-flow lesions, and histopathologically screened for the presence of microvessels, inflammation, thrombosis, or a combination of these. Immunohistochemistry was performed with endoglin (CD105), von Willebrand factor, and fibrinogen antibodies.
  
  
  RESULTS
  Clinically, 37 AVMs were classified as high-flow lesions and 43 as low-flow lesions. In 81% of high-flow lesions microvascular proliferations were seen versus in 14% of low-flow lesions (P < .005). In high-flow lesions, which were embolized before surgery (30% of all), 88% showed microvascular proliferation, 88% inflammation, and 33% thrombosis. However, similar vasoproliferative responses were also observed in nonembolized AVM (69% high-flow and 14% low-flow lesions). Endoglin was more frequently expressed in high-flow lesions. Extracellular von Willebrand factor staining was found in most lesions, irrespective of flow type or presence of microvascular proliferations.
  
  
  CONCLUSIONS
  The study was carried out at a single tertiary referral center.
  
  
  CONCLUSIONS
  Microvascular proliferative masses in AVMs appear to be strongly associated with high-flow characteristics. This could be explained to some extent by previous therapeutic embolization and/or inflammation in the lesion. However, occurrence of similar microvascular responses in AVM that were not embolized before surgery suggests that the biomechanical effects of high flow in these lesions may also have an angiogenic effect.
authors.affiliation: Department of Pathology, Symbiant/Medical Center Alkmaar, Alkmaar, The Netherlands; Department of Pathology, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Lorine B
authors.initials: LB
authors.lastname: Meijer-Jorna
authors.affiliation: Department of Pathology, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Chris M
authors.initials: CM
authors.lastname: van der Loos
authors.affiliation: Department of Pathology, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Onno J
authors.initials: OJ
authors.lastname: de Boer
authors.affiliation: Department of Molecular Cell Biology and Immunology, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Anton J G
authors.initials: AJG
authors.lastname: Horrevoets
authors.affiliation: Department of Dermatology, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Jan R
authors.initials: JR
authors.lastname: Mekkes
authors.affiliation: Department of Plastic and Reconstructive Surgery, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Chantal M A M
authors.initials: CMAM
authors.lastname: van der Horst
authors.affiliation: Department of Pathology, Academic Medical Center, Amsterdam, The Netherlands. Electronic address: a.c.vanderwal@amc.uva.nl.
authors.forename: Allard C
authors.initials: AC
authors.lastname: van der Wal
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001165:Arteriovenous Malformations / Q000473:pathology* / Q000503:physiopathology*; D001783:Blood Flow Velocity; D002648:Child; D002675:Child, Preschool; D004621:Embolization, Therapeutic / Q000009:adverse effects*; D005260:Female; D006801:Humans; D007249:Inflammation / Q000150:complications*; D008297:Male; D055806:Microvessels / Q000473:pathology*; D008875:Middle Aged; D012189:Retrospective Studies; D055815:Young Adult