title: Diagnosis of mediastinal masses in dogs by flow cytometry.
abstract: BACKGROUND
  Biopsy of mediastinal masses can be invasive, but the procedure may be necessary if cytology of a mass aspirate is inconclusive. The 2 most common mediastinal masses, lymphoma and thymoma, may both be comprised of small lymphocytes. We investigated the ability of flow cytometry to distinguish between these 2 neoplasms.
  
  
  OBJECTIVE
  Flow cytometry of mediastinal mass aspirates may provide a definitive diagnosis of thymoma or lymphoma, reducing the need for biopsy.
  
  
  METHODS
  Dogs with mediastinal masses presenting to the Veterinary Teaching Hospital/Animal Cancer Center were included in the study.
  
  
  METHODS
  Aspirates obtained over 2 years that met the inclusion criteria (i.e. sufficient viable cells and a definitive diagnosis by means other than flow cytometry) were analyzed by flow cytometry to determine the percentage of cells expressing B- and T-cell markers, and co-expressing CD4 and CD8.
  
  
  RESULTS
  All cases of thymoma (n = 6) consisted of > or = 10% lymphocytes coexpressing CD4 and CD8, a phenotype that is characteristic of thymocytes, whereas 6 of 7 lymphomas contained <2% CD4+CD8+ lymphocytes. The CD4+CD8+ lymphoma could be readily distinguished flow cytometrically from thymoma by light scatter properties. The phenotypes of the remaining lymphomas were CD4+ T cell (4), CD34+ (1) and B cell (1).
  
  
  CONCLUSIONS
  Our studies demonstrate that flow cytometry is a useful tool for discriminating mediastinal masses. Lymphocyte-rich mediastinal masses could be unambiguously identified by flow cytometry in 13/13 cases.
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, USA.
authors.forename: Susan
authors.initials: S
authors.lastname: Lana
authors.forename: Susan
authors.initials: S
authors.lastname: Plaza
authors.forename: Kerri
authors.initials: K
authors.lastname: Hampe
authors.forename: Rob
authors.initials: R
authors.lastname: Burnett
authors.forename: Anne C
authors.initials: AC
authors.lastname: Avery
mesh_terms: D000818:Animals; D002277:Carcinoma / Q000175:diagnosis / Q000473:pathology / Q000662:veterinary*; D004273:DNA, Neoplasm / Q000737:chemistry / Q000235:genetics; D004283:Dog Diseases / Q000175:diagnosis / Q000473:pathology*; D004285:Dogs; D005260:Female; D005434:Flow Cytometry / Q000662:veterinary; D006651:Histocytochemistry / Q000662:veterinary; D016130:Immunophenotyping / Q000662:veterinary; D008223:Lymphoma / Q000175:diagnosis / Q000473:pathology / Q000662:veterinary*; D008297:Male; D008479:Mediastinal Neoplasms / Q000175:diagnosis / Q000473:pathology / Q000662:veterinary*; D016133:Polymerase Chain Reaction / Q000662:veterinary; D013945:Thymoma / Q000175:diagnosis / Q000473:pathology / Q000662:veterinary*
chemical_list: D004273:DNA, Neoplasm