title: Langerhans cells in squamous cell carcinoma vs. pseudoepitheliomatous hyperplasia of the skin.
abstract: BACKGROUND
  In clinical and histopathological practice, it is sometimes difficult to distinguish pseudoepitheliomatous hyperplasia (PEH) from squamous cell carcinoma (SCC) of the skin. Several studies have shown a low density of Langerhans cells in SCC of the skin, and recent research on cervical SCCs has suggested that the decreased density of dendritic cells is secondary to low E-cadherin expression. SCCs of the head and neck similarly have decreased E-cadherin expression, but E-cadherin expression is preserved in PEH. We hypothesized that PEH of the skin would have an increased number of Langerhans cells compared with SCC.
  
  
  METHODS
  We studied immunohistochemical expression of CD1a on paraffin-embedded tissue in 12 cases of SCC and 11 cases of PEH of the skin.
  
  
  RESULTS
  The number of Langerhans cells in SCCs vs. PEH was similar; in both types of lesions, the Langerhans cells were decreased in density compared with the normal flanking epidermis.
  
  
  CONCLUSIONS
  PEH has a decreased number of Langerhans cells compared with the normal epidermis. As SCCs also have decreased numbers of CD1a-positive cells, this stain is not useful in differentiating these two entities.
authors.affiliation: Department of Dermatology, Yale University School of Medicine, New Haven, CT 06510, USA.
authors.forename: Anjela
authors.initials: A
authors.lastname: Galan
authors.forename: Christine J
authors.initials: CJ
authors.lastname: Ko
mesh_terms: D018949:Antigens, CD1 / Q000378:metabolism*; D002294:Carcinoma, Squamous Cell / Q000473:pathology*; D003937:Diagnosis, Differential; D006801:Humans; D006965:Hyperplasia; D007150:Immunohistochemistry; D007801:Langerhans Cells / Q000378:metabolism*; D012867:Skin / Q000473:pathology*; D012878:Skin Neoplasms / Q000473:pathology*
chemical_list: D018949:Antigens, CD1; C419393:CD1a antigen