title: CD117 (KIT) is a useful immunohistochemical marker for differentiating porocarcinoma from squamous cell carcinoma.
abstract: BACKGROUND
  Distinguishing porocarcinoma from squamous cell carcinoma (SCC) is clinically significant but can pose a diagnostic dilemma. The present study sought to confirm the diagnostic utility of CD117 immunohistochemistry in distinguishing porocarcinoma from SCC and to examine histologic, carcinoembryonic antigen (CEA) immunohistochemical and CA19-9 immunohistochemical differences between these tumors.
  
  
  METHODS
  Immunostaining with anti-CD117, anti-CEA and anti-CA19-9 antibodies was performed for 22 porocarcinomas and 31 SCCs. The extent of CD117, CEA and CA19-9 staining was classified as negative (<1%), rarely positive (1-4%), focally positive (5-29%) or diffusely positive (30-100%). CD117 staining intensity was semi-quantitatively graded as weak, moderate or strong.
  
  
  RESULTS
  All (100%) porocarcinomas were positive for CD117, with mainly focal (8/22) or diffuse (11/22) and moderate (9/22) to strong (8/22) staining. In contrast, only 6 of 31 SCCs (19.4%) expressed CD117 focally, and this expression was limited to the basal layer of the tumor in four cases. CEA immunostaining highlighted the lumina of all 22 porocarcinomas; however, CEA expression was not significantly different between porocarcinomas and SCCs (100 vs. 71.0%, respectively). CA19-9 was not expressed in the lumina of 5 of 22 porocarcinomas.
  
  
  CONCLUSIONS
  Along with CEA, CD117 immunohistochemistry could be helpful in distinguishing porocarcinomas from SCCs.
authors.affiliation: Department of Diagnostic Pathology, Kainan Hospital, Yatomi, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Goto
authors.affiliation: Department of Dermatology, Hyogo Cancer Center, Akashi, Japan.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Takai
authors.affiliation: Sapporo Dermatopathology Institute, Sapporo, Japan.
authors.forename: Takaya
authors.initials: T
authors.lastname: Fukumoto
authors.affiliation: Sapporo Dermatopathology Institute, Sapporo, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Anan
authors.affiliation: Sapporo Dermatopathology Institute, Sapporo, Japan.
authors.forename: Tetsunori
authors.initials: T
authors.lastname: Kimura
authors.affiliation: Division of Dermatology, Musashi Kosugi-Hospital, Nippon Medical School, Kawasaki, Japan.
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Ansai
authors.affiliation: Department of Dermatology, Kainan Hospital, Yatomi, Japan.
authors.forename: Yoshimi
authors.initials: Y
authors.lastname: Oshitani
authors.affiliation: Department of Dermatology, Hyogo Cancer Center, Akashi, Japan.
authors.forename: Yozo
authors.initials: Y
authors.lastname: Murata
authors.affiliation: Department of Diagnostic Pathology, Hyogo Cancer Center, Akashi, Japan.
authors.forename: Toshiko
authors.initials: T
authors.lastname: Sakuma
authors.affiliation: Department of Diagnostic Pathology, Hyogo Cancer Center, Akashi, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Hirose
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000378:metabolism*; D002294:Carcinoma, Squamous Cell / Q000378:metabolism / Q000473:pathology; D057090:Eccrine Porocarcinoma / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D008875:Middle Aged; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism*; D012189:Retrospective Studies; D013544:Sweat Gland Neoplasms / Q000378:metabolism / Q000473:pathology
chemical_list: D014408:Biomarkers, Tumor; D019009:Proto-Oncogene Proteins c-kit
keywords: CD117; c-KIT protein; cutaneous squamous cell carcinoma; immunohistochemistry; porocarcinoma