title: CD34 expression in desmoplastic melanoma.
abstract: BACKGROUND
  Primary and metastatic malignant melanoma can simulate various soft tissue tumors, including dermatofibrosarcoma protuberans (DFSP). Expression of CD34, a marker characteristic of DFSP, as well as other spindle cell tumors, has not been previously documented in malignant melanoma.
  
  
  METHODS
  We present here an unusual case of metastatic malignant melanoma with a strong histologic resemblance to DFSP and also CD34 expression.
  
  
  RESULTS
  The patient, a 72-year-old man with a history of an invasive malignant melanoma of the skin of the right lower abdomen, presented with a right axillary mass. Histologic sections revealed intersecting fascicles of spindle cells with nuclear pleomorphism and numerous mitotic figures, diffusely infiltrating the adipose tissue in a pattern closely simulating that seen in DFSP. In other foci, epithelioid neoplastic cells with abundant cytoplasm, prominent nucleoli, nuclear pseudoinclusions, and focal cytoplasmic melanin pigment were seen. The neoplastic spindle cells were strongly labeled by two anti-CD34 monoclonal antibodies. Some of the spindle cells and the majority of the epithelioid neoplastic cells expressed S-100 protein and focally tyrosinase. The tumor cells were negative for HMB-45 and MART-1. Melanosomes were not identified by electron microscopy.
  
  
  CONCLUSIONS
  This case demonstrates the potential of melanoma to simulate DFSP closely, on both morphologic and immunohistochemical grounds, and confirms the utility of employing a broad panel of immunohistochemical reagents in problematic cases.
authors.affiliation: Department of Pathology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9073, USA. mai.hoang@UTSouthwestern.edu
authors.forename: M P
authors.initials: MP
authors.lastname: Hoang
authors.forename: M A
authors.initials: MA
authors.lastname: Selim
authors.forename: R C
authors.initials: RC
authors.lastname: Bentley
authors.forename: J L
authors.initials: JL
authors.lastname: Burchette
authors.forename: C R
authors.initials: CR
authors.lastname: Shea
mesh_terms: D018952:Antigens, CD34 / Q000032:analysis*; D014408:Biomarkers, Tumor; D018223:Dermatofibrosarcoma / Q000737:chemistry / Q000473:pathology*; D003937:Diagnosis, Differential; D006801:Humans; D007150:Immunohistochemistry; D008545:Melanoma / Q000737:chemistry / Q000473:pathology*; D012878:Skin Neoplasms / Q000737:chemistry / Q000473:pathology*; D012983:Soft Tissue Neoplasms / Q000737:chemistry / Q000473:pathology
chemical_list: D018952:Antigens, CD34; D014408:Biomarkers, Tumor