title: A proposed classification for follicular involvement by melanoma.
abstract: BACKGROUND
  Folliculotropism in melanoma is poorly characterized and standard categorization for follicular involvement by melanoma is unavailable. We propose a logical categorization system.
  
  
  METHODS
  We conducted a search of our archives over a 24-year period for cases mentioning the terms follicle, follicular, folliculotropic, folliculocentric and melanoma.
  
  
  RESULTS
  We identified 90 cases of melanoma with involvement of the hair follicle. Distinct patterns were identified. The invasive patterns were primary follicular, folliculotropic and invasive arising from melanoma in situ (MIS) with extensive follicular involvement. Follicular involvement by MIS was either lentiginous, nested or a combination of both. A total of 29 invasive melanomas were identified. Of these 12 had invasive melanoma around the hair follicle, 2 were primary follicular melanomas, 7 showed folliculotropism and 3 were invasive melanomas arising from MIS around the follicle. Seventeen invasive melanomas had follicles only involved by MIS (9 nested, 6 nested and lentiginous and 2 lentiginous). A total of 61 cases of MIS with follicular involvement were identified; of these 33 were lentiginous, 10 nested and 18 both lentiginous and nested.
  
  
  CONCLUSIONS
  We propose that the three distinct patterns of follicular involvement by invasive melanoma and the three distinct patterns of MIS will be valuable for logically categorizing involvement of the hair follicle by melanoma.
authors: Department of Pathology, University of South Dakota - Sanford School of Medicine, Sioux Falls, SD, USA.
authors: B Joel
authors: BJ
authors: Tjarks
authors: Department of Dermatology, Cleveland Clinic, Cleveland, OH, USA.|Department of Dermatology, Indiana University School of Medicine, Indianapolis, IN, USA.
authors: Najwa
authors: N
authors: Somani
authors: Department of Dermatology, Cleveland Clinic, Cleveland, OH, USA.
authors: Melissa
authors: M
authors: Piliang
authors: Department of Dermatology, Cleveland Clinic, Cleveland, OH, USA.
authors: Wilma F
authors: WF
authors: Bergfeld
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006201:Hair Diseases / Q000145:classification* / Q000473:pathology; D018859:Hair Follicle / Q000473:pathology*; D006801:Humans; D008297:Male; D008545:Melanoma / Q000145:classification* / Q000473:pathology; D008875:Middle Aged; D012878:Skin Neoplasms / Q000145:classification* / Q000473:pathology; D000096142:Cutaneous Malignant Melanoma
keywords: dermatopathology; hair follicle; melanocytic neoplasm