title: Aberrant expression of HMB-45 in traumatized melanocytic nevi.
abstract: BACKGROUND
  Assessment of histologic and immunohistochemical maturation (with HMB-45 and anti-Ki-67) may be helpful in differentiating benign melanocytic nevi (BMN) from malignant melanoma. Recently, we reported loss of maturation and aberrant immunohistochemical findings in melanocytic nevi after liquid nitrogen cryotherapy (Adeniran et al, J Am Acad Dermatol 2009;61:341-5). Herein we report a similar phenomenon identified in traumatized melanocytic nevi (TMN).
  
  
  OBJECTIVE
  We sought to evaluate the histologic and immunohistochemical findings in early and late stages of traumatized nevi.
  
  
  METHODS
  Twenty-four cases of TMN were retrieved from the pathology archives. These were then assessed by two pathologists (T.L. and A.H.D.) using HMB-45 and MIB-1 (for Ki-67) antibodies.
  
  
  RESULTS
  TMN showed some of the following findings: epidermal changes (parakeratosis, ulceration, serum crust, flattening of the epidermis) and dermal changes including fibrosis and the presence of melanophages. In some cases, there was architectural disorder of the overlying melanocytes, with crowding in the basal layer, but without significant pagetoid spread. Occasionally, the dermal scar contained larger, more epithelioid-appearing melanocytes than those beneath the scar. Fifty-four percent of TMN lacked obvious immunohistochemical maturation with HMB-45, since nevus cells within the scar or directly beneath it were strongly labeled. None of the TMN showed appreciable labeling for Ki-67.
  
  
  CONCLUSIONS
  The exact clinical duration between trauma and biopsy could not be determined.
  
  
  CONCLUSIONS
  Loss of maturation with HMB-45 in TMN can be a diagnostic pitfall in challenging cases. Concurrent evaluation of MIB-1 expression, along with the characteristic histologic features of trauma, should allow the correct diagnosis to be reached.
authors.affiliation: Department of Pathology & Immunology, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Todd M
authors.initials: TM
authors.lastname: Leleux
authors.forename: Victor G
authors.initials: VG
authors.lastname: Prieto
authors.forename: A Hafeez
authors.initials: AH
authors.lastname: Diwan
mesh_terms: D049109:Cell Proliferation; D004817:Epidermis / Q000473:pathology; D005355:Fibrosis; D006801:Humans; D007150:Immunohistochemistry; D008544:Melanocytes / Q000473:pathology; D058950:Melanoma-Specific Antigens / Q000378:metabolism*; D009508:Nevus, Pigmented / Q000378:metabolism / Q000473:pathology*; D009584:Nitrogen / Q000009:adverse effects; D012878:Skin Neoplasms / Q000378:metabolism / Q000473:pathology*; D013194:Staining and Labeling; D058951:gp100 Melanoma Antigen
chemical_list: D058950:Melanoma-Specific Antigens; C548637:PMEL protein, human; D058951:gp100 Melanoma Antigen; D009584:Nitrogen