title: Giant cell collagenoma: case report and review of the literature.
abstract: BACKGROUND
  Giant cell collagenoma (GCC) is a recently described cutaneous fibrous neoplasm that usually affects young to middle-aged adults. Despite its similar histological appearance with circumscribed storiform collagenoma, no association of GCC with Cowden's syndrome has been described so far. To the best of our knowledge only five cases of this rare fibrous tumor have been reported so far.
  
  
  METHODS
  We report a case of a 79-year-old male patient presenting with a slow growing flesh-colored dome-shaped lesion in his left forearm, with a clinical diagnosis of fibroma. No stigma of Cowden's syndrome was depicted.
  
  
  RESULTS
  The histological analysis showed a symmetrical and well-circumscribed flat-dome-shaped lesion covered by an atrophic overlying epidermis. The neoplasm was composed of hyalinized collagen bundles disposed in a whorled storiform pattern. Admixed with the collagen matrix, there were two distinct cell populations, one composed by spindle-shaped mononuclear cells, and the other composed by bizarre multinucleated giant cells. Immunohistochemical analysis showed positivity for vimentin and actin HHF35 in the mononucleated. The multinucleated cells only immunoexpressed vimentin.
  
  
  CONCLUSIONS
  GCC is an unusual cutaneous fibrous tumor that should be differentiated from circumscribed storiform collagenoma, pleomorphic fibroma, regressive forms of dermatofibroma, and solitary myofibroma based on its histological features.
authors.affiliation: Salomão e Zoppi Associated Pathologist, São Paulo, Brazil.
authors.forename: Hugo
authors.initials: H
authors.lastname: Brito
authors.forename: Emílio M
authors.initials: EM
authors.lastname: Pereira
authors.forename: Jorge S
authors.initials: JS
authors.lastname: Reis-Filho
authors.forename: Sueli A
authors.initials: SA
authors.lastname: Maeda
mesh_terms: D000199:Actins / Q000032:analysis; D000368:Aged; D003094:Collagen / Q000032:analysis; D005350:Fibroma / Q000737:chemistry / Q000473:pathology* / Q000601:surgery; D015726:Giant Cells / Q000737:chemistry / Q000473:pathology; D006801:Humans; D007124:Immunoenzyme Techniques; D007963:Leukocytes, Mononuclear / Q000737:chemistry / Q000473:pathology; D008297:Male; D012598:Sclerosis / Q000473:pathology; D012878:Skin Neoplasms / Q000737:chemistry / Q000473:pathology* / Q000601:surgery; D014746:Vimentin / Q000032:analysis
chemical_list: D000199:Actins; D014746:Vimentin; D003094:Collagen