title: Immunohistochemical assessment of PTEN in vulvar cancer: best practices for tissue staining, evaluation, and clinical association.
abstract: BACKGROUND
  Pten encodes a well-characterized protein that is important in several cancers due to its tumor suppressor function. Yet, the detection and evaluation of PTEN by immunohistochemistry (IHC) for clinical practice have not been standardized. Thus, in this study, we performed a literature review of protocols for PTEN assessment by IHC and the possible differences in evaluation, based on our experience with vulvar carcinomas. Also, we report some of our most recent findings regarding the clinical impact of PTEN in this type of tumor.
  
  
  METHODS
  In total, 150 FFPE vulvar carcinoma samples in a tissue microarray were examined by IHC with regard to PTEN, PI3K, AKT, and mTOR. All evaluations were performed by slide digitalization and quantification using APERIO ImageScope software. All measurements were converted into HScore values for the statistical analysis.
  
  
  RESULTS
  Sharp and specific PTEN expression was observed in the nuclei and cytoplasmic compartments. Its HScore values ranged from 3.5 to 226, with a median of 92.5. mTOR expression was robust in all cases (mean HScore=248.1). AKT and PI3K had median HScore values of 200.5 and 156.5, respectively. In addition, PTEN expression was associated with higher rates of patient survival.
  
  
  CONCLUSIONS
  The preanalytical step is the first issue in the immunohistochemical evaluation of PTEN. With regard to the analytical procedure, the antigen retrieval step yielded better stains for protocols with high-pH buffers, and antibody clone 6H2.1 effected the most reliable results. PTEN is a good prognostic marker for vulvar cancer, correlating with higher rates of patient survival. Our data underscore the importance of technical standardization to ensure more reliable and reproducible evaluation of PTEN in clinical practice.
authors.affiliation: Molecular Morphology Group - Investigative Pathology Department, AC Camargo Cancer Center, Antonio Prudente St, 211, Liberdade, São Paulo, SP 01509-900, Brazil.
authors.forename: A M
authors.initials: AM
authors.lastname: Lavorato-Rocha
authors.affiliation: Molecular Morphology Group - Investigative Pathology Department, AC Camargo Cancer Center, Antonio Prudente St, 211, Liberdade, São Paulo, SP 01509-900, Brazil.
authors.forename: L G
authors.initials: LG
authors.lastname: Anjos
authors.affiliation: Molecular Morphology Group - Investigative Pathology Department, AC Camargo Cancer Center, Antonio Prudente St, 211, Liberdade, São Paulo, SP 01509-900, Brazil.
authors.forename: I W
authors.initials: IW
authors.lastname: Cunha
authors.affiliation: Molecular Morphology Group - Investigative Pathology Department, AC Camargo Cancer Center, Antonio Prudente St, 211, Liberdade, São Paulo, SP 01509-900, Brazil.
authors.forename: J
authors.initials: J
authors.lastname: Vassallo
authors.affiliation: Molecular Morphology Group - Investigative Pathology Department, AC Camargo Cancer Center, Antonio Prudente St, 211, Liberdade, São Paulo, SP 01509-900, Brazil.
authors.forename: F A
authors.initials: FA
authors.lastname: Soares
authors.affiliation: Molecular Morphology Group - Investigative Pathology Department, AC Camargo Cancer Center, Antonio Prudente St, 211, Liberdade, São Paulo, SP 01509-900, Brazil. Electronic address: rafael.malagoli@gmail.com.
authors.forename: R M
authors.initials: RM
authors.lastname: Rocha
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis* / Q000096:biosynthesis*; D005260:Female; D006801:Humans; D051059:PTEN Phosphohydrolase / Q000032:analysis* / Q000096:biosynthesis*; D013194:Staining and Labeling / Q000379:methods*; D015996:Survival Rate / Q000639:trends; D025521:Tumor Suppressor Proteins / Q000032:analysis*; D014846:Vulvar Neoplasms / Q000378:metabolism* / Q000401:mortality / Q000473:pathology*
chemical_list: D014408:Biomarkers, Tumor; D025521:Tumor Suppressor Proteins; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human
keywords: Immunohistochemistry; PTEN; Protocol; Vulvar cancer