title: New concepts on the histogenesis of eccrine neoplasia from keratin expression in the normal eccrine gland, syringoma and poroma.
abstract: BACKGROUND
  Peripheral and luminal layers of eccrine sweat gland ducts are self-renewing structures. Proliferation is restricted to the lowermost luminal layer, but randomly scattered in the peripheral layer. Each layer exhibits differential expression of keratins K5/K14 and K6/K16. Keratin K1 occurs only in peripheral cells and the novel keratin K77 is specific for luminal cells.
  
  
  OBJECTIVE
  To investigate the expression of luminal (K77), peripheral (K1) and further discriminatory keratins in two eccrine sweat gland tumours: syringoma, thought to show differentiation towards luminal cells of intraepidermal sweat ducts and eccrine poroma, considered to arise from poroid cells, i.e. peripheral duct cells; and keratinocytes of the lower acrosyringium/sweat duct ridge differentiating towards cells of intradermal/intraepidermal duct segments.
  
  
  METHODS
  Paraffin-embedded sections were examined by immunohistochemistry using several keratin, smooth muscle actin and Ki-67 antibodies.
  
  
  RESULTS
  We confirmed the ductal nature of syringomas. Despite drastic morphological alterations in both layers, their keratin patterns remained almost undisturbed compared with normal ducts. In eccrine poroma epidermal keratins K5/K14 were ubiquitously expressed in all poroid cells. Cell islands deviating morphologically from poroid cells contained epidermal keratins K1/K10. K77 expression was limited to luminal cells of intact duct structures within the tumours.
  
  
  CONCLUSIONS
  Syringomas are benign tumours of luminal cells of the lowermost intraglandular sweat duct. Poroid precursor cells of poromas do not comprise peripheral duct cells nor do poromas differentiate towards peripheral or luminal duct cells. Instead, poroid cells consist only of keratinocytes of the lowermost acrosyringium and the sweat duct ridge and poromas tend to differentiate towards the cells of the upper acrosyringium.
authors.affiliation: Division of Skin Carcinogenesis, German Cancer Research Centre, Heidelberg, Germany. langbein@dkfz.de
authors.forename: L
authors.initials: L
authors.lastname: Langbein
authors.forename: B
authors.initials: B
authors.lastname: Cribier
authors.forename: P
authors.initials: P
authors.lastname: Schirmacher
authors.forename: S
authors.initials: S
authors.lastname: Praetzel-Wunder
authors.forename: B
authors.initials: B
authors.lastname: Peltre
authors.forename: J
authors.initials: J
authors.lastname: Schweizer
mesh_terms: D006607:Adenoma, Sweat Gland / Q000737:chemistry* / Q000473:pathology; D014408:Biomarkers, Tumor / Q000032:analysis*; D004439:Eccrine Glands / Q000737:chemistry* / Q000473:pathology; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D007124:Immunoenzyme Techniques; D007150:Immunohistochemistry; D053556:Keratin-1 / Q000032:analysis*; D013544:Sweat Gland Neoplasms / Q000737:chemistry* / Q000473:pathology; D018252:Syringoma / Q000737:chemistry / Q000473:pathology
chemical_list: D014408:Biomarkers, Tumor; C491616:KRT1 protein, human; C486594:KRT77 protein, human; D053556:Keratin-1