title: [A case of primary cutaneous PEComa].
abstract: BACKGROUND
  PEComas (PEC: Perivascular epithelioid cell) are tumours expressing both melanocytic and myogenic markers. The clinical features are non-specific.
  
  
  METHODS
  A 55-year-old woman presented with a non-specific tumour on her right arm. Histological examination revealed an intradermal tumour composed of clear epithelial cells. The tumour was positive for HMB45 and protein S100, and was negative for Melan-A and actin. A diagnosis of PEComa was retained despite negative myogenic markers.
  
  
  CONCLUSIONS
  PEComas are neoplasms composed of nests and fascicles of clear to granular epithelioid cells that express both melanocytic markers (HMB45, Melan-A, NK1C3, tyrosinase) and myogenic markers (actin, caldesmin, desmin, calponin), whereas S100 protein and cytokeratins are usually absent. Included in this broad category are angiomyolipoma, clear-cell "sugar" tumours and lymphangioleiomyoma. Some deep PEComas may have a malignant course. Cutaneous primitive forms are exceptional and often benign. Histological differential diagnoses to consider are those of clear-cell tumours: paraganglioma-like dermal melanocytic tumour, melanoma, metastatic clear-cell renal carcinoma and epithelioid sarcoma. In our patient, a diagnosis of cutaneous primitive PEComa was retained despite the absence of myogenic markers and the positivity of the protein S100, based on the cytological and immunohistochemical features, which were not evocative of any other diagnosis.
  
  
  CONCLUSIONS
  Cutaneous PEComa are non-specific tumours. Histological analysis confirms the diagnosis and allows other more aggressive tumours to be ruled out.
authors.affiliation: Service de dermatologie, hôpital Beauregard, CHR de Metz-Thionville, 21, rue des Frères, 57100 Thionville, France. cecile_trotot29@hotmail.com
authors.forename: C
authors.initials: C
authors.lastname: Trotot-Voilliot
authors.forename: E
authors.initials: E
authors.lastname: Laveine
authors.forename: P
authors.initials: P
authors.lastname: Beurey
authors.forename: J-F
authors.initials: JF
authors.lastname: Cuny
authors.forename: J-L
authors.initials: JL
authors.lastname: Schmutz
authors.forename: F
authors.initials: F
authors.lastname: Truchetet
mesh_terms: D001132:Arm; D014408:Biomarkers, Tumor / Q000032:analysis; D002292:Carcinoma, Renal Cell / Q000175:diagnosis / Q000556:secondary; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D058950:Melanoma-Specific Antigens / Q000032:analysis; D008875:Middle Aged; D018321:Neurothekeoma / Q000175:diagnosis; D010235:Paraganglioma / Q000175:diagnosis; D054973:Perivascular Epithelioid Cell Neoplasms / Q000737:chemistry / Q000175:diagnosis* / Q000473:pathology / Q000601:surgery; D011379:Prognosis; D009418:S100 Proteins / Q000032:analysis; D012878:Skin Neoplasms / Q000737:chemistry / Q000175:diagnosis* / Q000473:pathology / Q000601:surgery; D058951:gp100 Melanoma Antigen
chemical_list: D014408:Biomarkers, Tumor; D058950:Melanoma-Specific Antigens; C548637:PMEL protein, human; D009418:S100 Proteins; D058951:gp100 Melanoma Antigen