title: The Role of p16, p21, p27, p53 and Ki-67 Expression in the Differential Diagnosis of Cutaneous Squamous Cell Carcinomas and Keratoacanthomas: An Immunohistochemical Study.
abstract: BACKGROUND
  Distinguishing squamous cell carcinoma (SCC) from keratoacanthoma (KA) by histopathological features may not be sufficient for a differential diagnosis, as KAs may, in some cases, imitate well-differentiated SCCs.
  
  
  OBJECTIVE
  In this study, we investigated whether the expression of the p16, p21, p27, p53 genes and a Ki-67 proliferation index are useful in distinguishing between these two tumors.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  Immunohistochemistry was used to investigate the expression of the p16, p21, p27, p53 genes and the Ki-67 proliferation index was investigated in well-differentiated SCC with KA-like features (n=40) and KA (n=30).
  
  
  RESULTS
  The results of all of the examined markers, except for p27 (p16, p21, p53, and Ki-67) were found to be significantly different between the SCC and KA samples (p<0.05).
  
  
  CONCLUSIONS
  In well-differentiated SCC with KA-like features and KA cases where the differential diagnosis is difficult from a histopathological perspective, the use of p16, p21, p53 expression and a Ki-67 proliferation index can be useful for the differential diagnosis of SCCs and KAs.
authors.affiliation: Department of Pathology, Recep Tayyip Erdoğan University School of Medicine, Rize, Turkey.
authors.forename: Recep
authors.initials: R
authors.lastname: Bedir
authors.affiliation: Department of Pathology, Recep Tayyip Erdoğan University School of Medicine, Rize, Turkey.
authors.forename: Hasan
authors.initials: H
authors.lastname: Güçer
authors.affiliation: Department of Pathology, Recep Tayyip Erdoğan University School of Medicine, Rize, Turkey.
authors.forename: İbrahim
authors.initials: İ
authors.lastname: Şehitoğlu
authors.affiliation: Department of Pathology, Recep Tayyip Erdoğan University School of Medicine, Rize, Turkey.
authors.forename: Cüneyt
authors.initials: C
authors.lastname: Yurdakul
authors.affiliation: Department of Pathology, Marmara University School of Medicine, İstanbul, Turkey.
authors.forename: Pelin
authors.initials: P
authors.lastname: Bağcı
authors.affiliation: Clinic of Dermatology, Rize State Hospital, Rize, Turkey.
authors.forename: Pelin
authors.initials: P
authors.lastname: Üstüner
keywords: Differential diagnosis; immunohistochemistry; keratoacanthoma; skin; squamous cell carcinoma