title: Flow-cytometric diagnosis of thymoma using needle biopsy specimens.
abstract: BACKGROUND
  Thymoma is a neoplasm of thymic epithelial cells which is characteristically associated with a large number of non-neoplastic T lymphocytes. These T cells are induced by epithelial cells and show a unique phenotype of CD4(+)8(+) double positive (DP), when studied by flow cytometry. This DP phenotype can be used as one of the diagnostic criteria to indicate a thymoma. The preoperative diagnosis of thymoma and other thymic tumors is an important problem because the treatment differs according to the diagnosis.
  
  
  METHODS
  A flow-cytometric analysis of needle biopsy specimens was performed on ten thymic tumors. The results were then compared with the findings of a histological diagnosis using conventional hematoxylin-eosin (H&E) staining.
  
  
  RESULTS
  Six cases with high frequencies of DP cells were diagnosed as thymoma by a flow-cytometric analysis, and were confirmed by a histological analysis of the resected specimen. Flow cytometry did not suggest a thymoma in the other four cases with few DP cells. The final diagnoses of the resected specimen of these four cases were: one thymic carcinoma, one malignant lymphoma, and two germ-cell tumors. The accuracy and specificity of diagnosis of thymoma using a fluorescence-activated cell sorting analysis from needle biopsy specimens were 6/6 (100%). On the other hand, the specificity of H&E staining from needle biopsy specimens for the diagnosis of thymoma was 6/6 (100%), but the accuracy was only 6/9 (66.7%).
  
  
  CONCLUSIONS
  Flow cytometry can be applied to needle biopsy specimens and thus is considered to offer useful information for the preoperative diagnosis of thymic tumors.
authors.affiliation: Department of Surgery II, Nagoya City University Medical School, 1 Kawasumi, Mizuho-ku, Japan.
authors.forename: Tomoki
authors.initials: T
authors.lastname: Yokoyama
authors.forename: Masayuki
authors.initials: M
authors.lastname: Tanahashi
authors.forename: Hisashi
authors.initials: H
authors.lastname: Tateyama
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Yamakawa
authors.forename: Masanobu
authors.initials: M
authors.lastname: Kiriyama
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Fujii
mesh_terms: D000328:Adult; D001707:Biopsy, Needle; D015496:CD4-Positive T-Lymphocytes / Q000473:pathology; D018414:CD8-Positive T-Lymphocytes / Q000473:pathology; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D012680:Sensitivity and Specificity; D013945:Thymoma / Q000473:pathology*; D013950:Thymus Gland / Q000473:pathology; D013953:Thymus Neoplasms / Q000473:pathology*