title: PD-L1 expression in cutaneous squamous cell carcinoma correlates with risk of metastasis.
abstract: BACKGROUND
  Programmed cell death ligand 1 (PD-L1) expression in primary cutaneous squamous cell carcinoma has not been described.
  
  
  METHODS
  We reviewed immunohistochemical stained sections of 40 primary and five metastatic cutaneous squamous cell carcinomas using antibody to PD-L1 and classified the staining pattern according to the DAKO tumor proportion score method. We compared the staining results with microscopic staging parameters associated with risk of metastasis including tumor diameter, histologic grade, tumor thickness and perineural invasion.
  
  
  RESULTS
  PD-L1 expression was present in 4 of 20 low risk tumors (20%), all of which showed low expression. PD-L1 expression was present in 14 of 20 high risk tumors (70%), 12 of which showed low expression and 2 of which showed high expression, 5 of 5 metastases (100%), with three showing low expression and two showing high expression.
  
  
  CONCLUSIONS
  This survey documents PD-L1 expression in cutaneous squamous cell carcinoma and shows a positive correlation between the degree PD-L1 expression and pathologic findings related to risk of metastasis including large diameter, higher histological grade and tumor thickness.
authors.affiliation: University of Tennessee Graduate School of Medicine, Department of Internal Medicine, Knoxville, TN, USA.
authors.forename: Nathaniel A
authors.initials: NA
authors.lastname: Slater
authors.affiliation: Knoxville Dermatopathology Laboratory, Knoxville, TN, USA.|Vanderbilt University, Department of Pathology, Nashville, TN, USA.|University of Tennessee Graduate School of Medicine, Department of Pathology, Knoxville, TN, USA.
authors.forename: Paul B
authors.identifier: http://orcid.org/0000-0002-9185-3548
authors.initials: PB
authors.lastname: Googe
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D060890:B7-H1 Antigen / Q000032:analysis / Q000096:biosynthesis*; D014408:Biomarkers, Tumor / Q000032:analysis*; D002294:Carcinoma, Squamous Cell / Q000473:pathology*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness / Q000473:pathology; D012189:Retrospective Studies; D012878:Skin Neoplasms / Q000473:pathology*; D055815:Young Adult
chemical_list: D060890:B7-H1 Antigen; D014408:Biomarkers, Tumor; C423236:CD274 protein, human
keywords: PD-L1; cutaneous squamous cell carcinoma; immunohistochemistry; programmed cell death ligand 1; risk of metastasis