title: A morphometric and immunohistochemical study of melanocytes in periorbital hyperpigmentation.
abstract: BACKGROUND
  An increase in number of melanocytes in the basal cell layer of the epidermis is an important feature in many disorders of hyperpigmentation. In this study, we attempted an objective evaluation of the linear density of melanocytes and keratinocytes, along with other epidermal characteristics, in periorbital hyperpigmentation using immunohistochemistry and morphometric techniques.
  
  
  METHODS
  Melanocytes and epidermal parameters were assessed by digital morphometry in 30 newly diagnosed cases of periorbital hyperpigmentation and 14 controls from the post-auricular region. Melanocytes were labelled with the immunohistochemical stains, Melan-A and tyrosinase. We studied the linear keratinocyte density, mean linear melanocyte density, ratio of melanocytes to keratinocytes, the ratio between inner and outer epidermal length, maximum epidermal thickness and minimum epidermal thickness.
  
  
  RESULTS
  Melan-A expression of melanocytes showed strong positive correlation (r=0.883) with the tyrosinase expression. Mean linear melanocyte density was 24/mm (range: 13-30/mm) in cases and 17/mm (13-21/mm) in controls and this difference was statistically significant (P<0.001). The mean ratio of melanocyte to keratinocyte was 0.22 (0.12-0.29) in cases and 0.16 (0.12-0.21) in controls; again, this difference was statistically significant (P<0.001). There was a mild negative correlation with linear keratinocyte density (r=-0.302) and the ratio between inner and outer epidermal length (r=-0.456). However, there were no differences in epidermal thicknesses.
  
  
  CONCLUSIONS
  There were fewer control biopsies than optimal, and they were not taken from the uninvolved periorbital region.
  
  
  CONCLUSIONS
  Mean linear melanocyte density and the ratio of melanocytes to keratinocytes is increased in cases with periorbital hyperpigmentation. It is, therefore, likely that increased melanocyte density may be the key factor in the pathogenesis of periorbital hyperpigmentation.
authors.affiliation: Department of Pathology, Armed Forces Medical College, Pune, Maharashtra, India.
authors.forename: Dibyajyoti
authors.initials: D
authors.lastname: Boruah
authors.forename: V
authors.initials: V
authors.lastname: Manu
authors.forename: Ajay
authors.initials: A
authors.lastname: Malik
authors.forename: Manas
authors.initials: M
authors.lastname: Chatterjee
authors.forename: Biju
authors.initials: B
authors.lastname: Vasudevan
authors.forename: V
authors.initials: V
authors.lastname: Srinivas
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D002452:Cell Count; D004817:Epidermis / Q000473:pathology*; D005123:Eye; D005148:Facial Dermatoses / Q000473:pathology*; D005260:Female; D006801:Humans; D017495:Hyperpigmentation / Q000473:pathology*; D007150:Immunohistochemistry; D015603:Keratinocytes / Q000473:pathology; D058965:MART-1 Antigen / Q000032:analysis; D008297:Male; D008544:Melanocytes / Q000737:chemistry* / Q000473:pathology*; D008875:Middle Aged; D014442:Monophenol Monooxygenase / Q000032:analysis; D055815:Young Adult
chemical_list: D058965:MART-1 Antigen; D014442:Monophenol Monooxygenase