title: Cytologic diagnosis of rhabdomyosarcoma in a child with a pleural effusion. A case report.
abstract: BACKGROUND
  A pleural effusion in children is usually caused by infectious diseases; malignant effusion is very uncommon. In a case of a malignant effusion in a child, a pleura-based metastasis of a neoplasm with a typically high prevalence in childhood has to be considered. Examples are neuroblastoma, nephroblastoma, Wilms' tumor, hepatoblastoma, malignant germ cell tumor and rhabdomyosarcoma.
  
  
  METHODS
  A 4-year old boy presented with a unilateral pleural effusion. Cytologic examination of the effusion revealed malignant small round cells admixed with very large cells with atypical nuclei. In formalin-fixed cell blocks prepared for immunocytochemistry the cells expressed desmin and myf-4. The cytologic diagnosis was consistent with metastatic rhabdomyosarcoma. Subsequent computed tomography revealed a mass above the diaphragm, which was biopsied. Histologic examination of a needle biopsy specimen confirmed the diagnosis of rhabdomyosarcoma. Molecular examination revealed a PAX3-FKHR fusion transcript specific to the alveolar type of rhabdomyosarcoma.
  
  
  CONCLUSIONS
  This case illustrates the usefulness of immunocytochemistry on cell block preparations in diagnosing difficult cases of effusion cytology.
authors.affiliation: Department of Pathology, Atrium Medical Centre, P.O. Box 4446, 6401CX Heerlen, The Netherlands. p.theunissen@gozl.nl
authors.forename: Paul
authors.initials: P
authors.lastname: Theunissen
authors.forename: Martin
authors.initials: M
authors.lastname: Cremers
authors.forename: Syb
authors.initials: S
authors.lastname: van der Meer
authors.forename: Freek
authors.initials: F
authors.lastname: Bot
authors.forename: Johannes
authors.initials: J
authors.lastname: Bras
mesh_terms: D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism; D002675:Child, Preschool; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D003937:Diagnosis, Differential; D006801:Humans; D007150:Immunohistochemistry; D008168:Lung / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000235:genetics / Q000556:secondary*; D008297:Male; D015514:Oncogene Proteins, Fusion / Q000235:genetics / Q000378:metabolism; D000072041:PAX3 Transcription Factor; D051761:Paired Box Transcription Factors; D016066:Pleural Effusion, Malignant / Q000473:pathology*; D011859:Radiography; D018232:Rhabdomyosarcoma, Alveolar / Q000000981:diagnostic imaging / Q000235:genetics / Q000556:secondary*; D014157:Transcription Factors
chemical_list: D014408:Biomarkers, Tumor; D004268:DNA-Binding Proteins; D015514:Oncogene Proteins, Fusion; D000072041:PAX3 Transcription Factor; C489409:PAX3 protein, human; D051761:Paired Box Transcription Factors; D014157:Transcription Factors; C068686:Pax3 protein, mouse