title: Dense pattern of embryonal rhabdomyosarcoma, a lesion easily confused with alveolar rhabdomyosarcoma: a report from the Soft Tissue Sarcoma Committee of the Children's Oncology Group.
abstract: OBJECTIVE
  To examine whether the frequency of fusion-negative alveolar rhabdomyosarcoma (ARMSn) increased coincident with changes in the definition of alveolar histology.
  
  
  METHODS
  We re-reviewed alveolar rhabdomyosarcoma (ARMS) in the Children's Oncology Group study D9803, comparing histopathology with fusion status.
  
  
  RESULTS
  Our review of 255 original ARMS cases (compared with a control group of 38 embryonal rhabdomyosarcomas [ERMS] cases) revealed that many had an ARMS-like densely cellular pattern with cytologic features and myogenin expression more typical of ERMS. Following re-review, 84 (33%) cases of original ARMS were rediagnosed as ERMS. All reclassified ERMS, including dense ERMS, were fusion negative, whereas 82% of confirmed ARMS cases were fusion positive. Total ARMS diagnoses returned to historic rates of 25% to 30% of all rhabdomyosarcomas, and ARMSn decreased from 37% to 18% of ARMS cases. The outcome of reclassified ERMS was similar to confirmed ERMS.
  
  
  CONCLUSIONS
  To address the role of fusion status in risk stratification, pathologists should include both a histologic diagnosis and an evaluation of fusion status for all new ARMS diagnoses.
authors.affiliation: Seattle Children's Hospital, Department of Laboratories, M/S OC.8.720, 4800 Sandpoint Way NE, Seattle, WA 98015, USA. erin.rudzinski@seattlechildrens.org
authors.forename: Erin R
authors.initials: ER
authors.lastname: Rudzinski
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Teot
authors.forename: James R
authors.initials: JR
authors.lastname: Anderson
authors.forename: Julie
authors.initials: J
authors.lastname: Moore
authors.forename: Julia A
authors.initials: JA
authors.lastname: Bridge
authors.forename: Frederic G
authors.initials: FG
authors.lastname: Barr
authors.forename: Julie M
authors.initials: JM
authors.lastname: Gastier-Foster
authors.forename: Stephen X
authors.initials: SX
authors.lastname: Skapek
authors.forename: Douglas S
authors.initials: DS
authors.lastname: Hawkins
authors.forename: David M
authors.initials: DM
authors.lastname: Parham
mesh_terms: D002648:Child; D003937:Diagnosis, Differential; D018572:Disease-Free Survival; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors / Q000235:genetics; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D018008:Myogenin / Q000378:metabolism*; D009820:Ohio; D015514:Oncogene Proteins, Fusion / Q000235:genetics*; D000072041:PAX3 Transcription Factor; D051763:PAX7 Transcription Factor / Q000235:genetics; D051761:Paired Box Transcription Factors / Q000235:genetics*; D016612:Paraffin Embedding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018232:Rhabdomyosarcoma, Alveolar / Q000145:classification* / Q000378:metabolism / Q000473:pathology; D018233:Rhabdomyosarcoma, Embryonal / Q000145:classification* / Q000378:metabolism / Q000473:pathology; D012509:Sarcoma / Q000145:classification* / Q000378:metabolism / Q000473:pathology; D016019:Survival Analysis; D014565:Urogenital Neoplasms / Q000145:classification* / Q000378:metabolism / Q000473:pathology
chemical_list: C085126:FOXO1 protein, human; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; D018008:Myogenin; D015514:Oncogene Proteins, Fusion; D000072041:PAX3 Transcription Factor; C489409:PAX3 protein, human; C471563:PAX3-FOXO1A fusion protein, human; D051763:PAX7 Transcription Factor; C497321:PAX7 protein, human; D051761:Paired Box Transcription Factors
keywords: Alveolar rhabdomyosarcoma; Embryonal rhabdomyosarcoma; Histologic classification; Myogenin; Rhabdomyosarcoma