title: Tyrosinase expression in malignant melanoma, desmoplastic melanoma, and peripheral nerve tumors.
abstract: BACKGROUND
  Pathologists may encounter problems in the differential diagnosis of malignant melanoma, spindle and epithelioid neoplasms of peripheral nerves, and fibrohistiocytic tumors. Tyrosinase has been demonstrated to be a sensitive marker for melanoma.
  
  
  OBJECTIVE
  To determine the specificity of tyrosinase expression in the differential diagnosis of melanoma, desmoplastic melanoma, and peripheral nerve sheath tumors.
  
  
  METHODS
  Immunoreactivity for tyrosinase, HMB-45 (anti-gp100 protein), S100 protein, CD34, and vimentin was studied in 70 tumors, including 15 melanomas (5 desmoplastic, 4 amelanotic, 6 melanotic), 13 malignant peripheral nerve sheath tumors; 10 schwannomas (1 pigmented), 12 neurofibromas (4 pigmented), and 20 fibrohistiocytic tumors (10 dermatofibrosarcoma protuberans and 10 dermatofibromas). Microwave-based antigen retrieval was performed in 10mM citrate buffer, pH 6.0, for 20 minutes at 121 degrees C.
  
  
  RESULTS
  All melanomas demonstrated positive immunostaining for tyrosinase, HMB-45, and S100 protein. Immunoreactivity for HMB-45 was generally stronger than that for tyrosinase in amelanotic lesions and significantly stronger in 1 of the desmoplastic lesions. The 4 pigmented neurofibromas were focally positive for tyrosinase, but did not stain for HMB-45. The pigmented schwannoma was focally positive for both tyrosinase and HMB-45. The malignant peripheral nerve sheath tumors, dermatofibrosarcoma protuberans, and dermatofibromas were nonreactive for tyrosinase and HMB-45.
  
  
  CONCLUSIONS
  Our results support the sensitivity of tyrosinase expression and demonstrate the relative specificity of tyrosinase as a marker for melanocytic lesions, including desmoplastic melanoma, although pigmented peripheral nerve tumors may demonstrate focal positive staining. Immunoreactivity for tyrosinase and HMB-45 may have been enhanced by the microwave-based antigen-retrieval technique used in this study.
authors.affiliation: Department of Pathology, Pennsylvania Hospital, Philadelphia, PA 19107, USA.
authors.forename: Jenny L
authors.initials: JL
authors.lastname: Boyle
authors.forename: Helen M
authors.initials: HM
authors.lastname: Haupt
authors.forename: Jere B
authors.initials: JB
authors.lastname: Stern
authors.forename: Hinke A B
authors.initials: HA
authors.lastname: Multhaupt
mesh_terms: D018952:Antigens, CD34 / Q000032:analysis; D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor / Q000032:analysis; D018223:Dermatofibrosarcoma / Q000737:chemistry / Q000201:enzymology* / Q000556:secondary; D003937:Diagnosis, Differential; D006801:Humans; D007124:Immunoenzyme Techniques; D008545:Melanoma / Q000737:chemistry / Q000201:enzymology* / Q000556:secondary; D058950:Melanoma-Specific Antigens; D014442:Monophenol Monooxygenase / Q000032:analysis / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000032:analysis; D018317:Nerve Sheath Neoplasms / Q000737:chemistry / Q000201:enzymology* / Q000556:secondary; D009418:S100 Proteins / Q000032:analysis; D012878:Skin Neoplasms / Q000737:chemistry / Q000201:enzymology* / Q000473:pathology; D014746:Vimentin / Q000032:analysis
chemical_list: D018952:Antigens, CD34; D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D058950:Melanoma-Specific Antigens; D009363:Neoplasm Proteins; D009418:S100 Proteins; D014746:Vimentin; D014442:Monophenol Monooxygenase