title: Immunohistochemical evaluation of p16 expression in cutaneous histiocytic, fibrohistiocytic and undifferentiated lesions.
abstract: BACKGROUND
  Expression of p16 is frequently evaluated in melanocytic lesions. Expression of p16 in cutaneous histiocytic, fibrohistiocytic and undifferentiated lesions has not been well characterized.
  
  
  METHODS
  We evaluated p16 expression in a cohort of histiocytic (reticulohistiocytoma, Langerhans cell histiocytosis, xanthogranuloma, Rosai Dorfman disease and xanthoma), fibrohistiocytic (dermatofibroma, epithelioid fibrous histiocytoma and dermatofibrosarcoma protuberans) and undifferentiated (atypical fibroxanthoma and pleomorphic undifferentiated sarcoma) lesions. A group of melanocytic lesions (Spitz nevus, ordinary nevus, spitzoid melanoma and non-spitzoid melanoma) were also evaluated as reference. Each case was scored by the proportion of p16-positive cells and by staining intensity.
  
  
  RESULTS
  Immunoreactivity for p16 was found in almost all histiocytic (28/30, 93%) and fibrohistiocytic (22/24, 92%) lesions. About half of the undifferentiated lesions also exhibited p16 staining (9/17, 53%). Most of the melanocytic cases examined in this study expressed p16. A wide range of staining intensity and proportion of p16-positive cells was observed in most groups.
  
  
  CONCLUSIONS
  Expression of p16 is common, albeit variable in proportion and intensity, amongst a wide variety of cutaneous histiocytic, fibrohistiocytic and undifferentiated lesions. Further studies are required to determine if p16 expression is useful in distinguishing benign from malignant neoplasms of these types.
authors.affiliation: Department of Dermatology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Emily H
authors.initials: EH
authors.lastname: Smith
authors.affiliation: Department of Dermatology, University of Michigan, Ann Arbor, MI, USA.|Department of Pathology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Lori
authors.initials: L
authors.lastname: Lowe
authors.affiliation: Department of Dermatology, University of Michigan, Ann Arbor, MI, USA.|Department of Pathology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Paul W
authors.initials: PW
authors.lastname: Harms
authors.affiliation: Department of Dermatology, University of Michigan, Ann Arbor, MI, USA.|Department of Pathology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Fullen
authors.affiliation: Department of Dermatology, University of Michigan, Ann Arbor, MI, USA.|Department of Pathology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: May P
authors.initials: MP
authors.lastname: Chan
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis*; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050763:Cyclin-Dependent Kinase Inhibitor p18 / Q000032:analysis / Q000096:biosynthesis*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D012878:Skin Neoplasms / Q000175:diagnosis*; D055815:Young Adult
chemical_list: D014408:Biomarkers, Tumor; C000614131:CDKN2A protein, human; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050763:Cyclin-Dependent Kinase Inhibitor p18
keywords: histiocytosis; immunohistochemistry; melanocytic lesions; non-Langerhans cell; p16 protein