title: Identifying colorectal metastases in liver biopsies: the novel CDX2 antibody is less specific than the cytokeratin 20+/7- phenotype.
abstract: BACKGROUND
  Immunohistochemistry plays an important role in tracing the primary site in metastatic tumors of unknown origin. Therefore, determining the cytokeratin (CK) 20/CK7 pattern of metastases is one of the most helpful procedures as the CK20+/CK7- pattern is typical of colorectal adenocarcinomas. Expression of CDX2 protein is a new, highly specific and sensitive marker of the intestinal origin of adenocarcinomas. In the present study we compared the sensitivity and specificity of CDX2 expression and the CK20+/CK7- phenotype in predicting the colorectal origin of liver metastases.
  
  
  METHODS
  The study was carried out on a consecutive series of 125 core-needle biopsies of metastatic adenocarcinomas of the liver. Most of the patients were followed up to death, and primary tumor localization could be established in 102 cases by a combination of clinical, radiological, histological and, in some cases, autopsy data. All the needle biopsies were immunohistochemically stained for CK7, CK20 and CDX2. CDX2 expression (at 10% and 50% cut-off levels) and the CK20/CK7 pattern of the metastases were correlated to the primary site established.
  
  
  RESULTS
  The CK20+/CK7- pattern showed a specificity of 98.7% in predicting colorectal primary localization, which was superior to that of CDX2 expression at both cut-off levels (90% and 95.3% respectively). The sensitivity of CDX2 expression in these circumstances was 84% at the 10% cut-off, somewhat higher than that of the CK20+/CK7- phenotype (79.5%), but lower at the 50% cut-off level (72.7%).
  
  
  CONCLUSIONS
  The CK20+/CK7- immunophenotype is more specific in predicting the colorectal origin of liver metastasis than CDX2 expression.
authors.affiliation: Department of Pathology and Clinical Cytology, Central Hospital, Falun, Sweden. tibor.tot@ltdalarna.se
authors.forename: Tibor
authors.initials: T
authors.lastname: Tot
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000906:Antibodies / Q000737:chemistry; D000071616:CDX2 Transcription Factor; D015179:Colorectal Neoplasms / Q000473:pathology*; D005260:Female; D018398:Homeodomain Proteins / Q000276:immunology*; D006801:Humans; D007150:Immunohistochemistry; D016130:Immunophenotyping; D007381:Intermediate Filament Proteins / Q000096:biosynthesis*; D053554:Keratin-20; D053552:Keratin-7; D007633:Keratins / Q000096:biosynthesis*; D008113:Liver Neoplasms / Q000556:secondary*; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D010641:Phenotype; D012680:Sensitivity and Specificity; D015534:Trans-Activators
chemical_list: D000906:Antibodies; D000071616:CDX2 Transcription Factor; D018398:Homeodomain Proteins; D007381:Intermediate Filament Proteins; C507499:KRT20 protein, human; C507497:KRT7 protein, human; D053554:Keratin-20; D053552:Keratin-7; D015534:Trans-Activators; D007633:Keratins