title: Hemangiopericytoma in children and infants.
abstract: BACKGROUND
  Hemangiopericytoma (HPC) is a soft-tissue neoplasm most commonly seen in adults; only 5-10% of cases occur in children. Childhood HPC comprises two distinct clinical entities. In children older than 1 year, it behaves in a manner similar to adult HPC. Infantile HPC, however, although histologically identical to adult HPC, has a more benign clinical course. The reasons for these differences in the natural history of HPC are not well understood.
  
  
  METHODS
  The authors reviewed the clinicopathologic features of HPC as well as the treatment and outcomes of the 12 children (9 males and 3 females) treated for this disease at St. Jude Children's Research Hospital over a 35-year period.
  
  
  RESULTS
  At diagnosis, 9 patients were older than 1 year and 3 were younger than 1 year. Among the 9 older patients, tumors were most commonly found in the lower extremities (n = 5). One patient had been treated for acute lymphoblastic leukemia 15 years earlier. One patient had metastatic disease at diagnosis, and three had unresectable tumors. Two patients experienced objective responses to chemotherapy. Three patients died of disease progression. Among the three infants, two had unresectable disease at diagnosis, and both experienced excellent responses to neoadjuvant chemotherapy. In one case, the response of the tumor to chemotherapy correlated with maturation to hemangioma. All three infants are alive without evidence of disease.
  
  
  CONCLUSIONS
  HPC in children older than 1 year does not differ from adult HPC, and aggressive multimodality therapy is required. Infantile HPC, on the other hand, is characterized by better clinical behavior, with documented chemoresponsiveness and spontaneous regression, and requires a more conservative surgical approach. In some cases of infantile HPC, this benign behavior correlates with maturation to hemangioma.
authors.affiliation: Department of Hematology-Oncology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105-2794, USA.
authors.forename: C
authors.initials: C
authors.lastname: Rodriguez-Galindo
authors.forename: K
authors.initials: K
authors.lastname: Ramsey
authors.forename: J J
authors.initials: JJ
authors.lastname: Jenkins
authors.forename: C A
authors.initials: CA
authors.lastname: Poquette
authors.forename: S C
authors.initials: SC
authors.lastname: Kaste
authors.forename: T E
authors.initials: TE
authors.lastname: Merchant
authors.forename: B N
authors.initials: BN
authors.lastname: Rao
authors.forename: C B
authors.initials: CB
authors.lastname: Pratt
authors.forename: A S
authors.initials: AS
authors.lastname: Pappo
mesh_terms: D002648:Child; D002675:Child, Preschool; D003131:Combined Modality Therapy; D005260:Female; D006393:Hemangiopericytoma / Q000473:pathology / Q000628:therapy; D006801:Humans; D007223:Infant; D008279:Magnetic Resonance Imaging; D008297:Male; D008499:Medical Records; D009367:Neoplasm Staging; D012189:Retrospective Studies; D016879:Salvage Therapy; D016896:Treatment Outcome