Perivascular epithelioid cell neoplasms (PEComas): four malignant cases expanding the histopathological spectrum and a description of a unique finding

Virchows Arch. 2007 Apr;450(4):463-70. doi: 10.1007/s00428-007-0378-7. Epub 2007 Feb 15.


Four cases of malignant PEComas were stained with smooth muscle actin, muscle specific actin, desmin, human melanoma black-45, melan-A, microphthalmia transcription factor, S100 and cyclin D1. One case was studied by electron microscopy (EM). Tumour locations were the thigh, elbow, retroperitoneum and bladder in association with a urachal cyst. There were two men and two women; the average age was 51.3 years, and the size ranged from 5.0-23.0 cm. In three cases, 50-95% of the tumour was composed of pleomorphic sarcomatous areas. All cases had at least focal clear-cell areas. One case showed a continuous single layer of perivascular clear cells remote from the tumour, transitioning to invasive nests and to PEComa. EM demonstrated these cells in apposition to and in direct contact with the abluminal surface of the basal lamina of the capillaries. We suggest the term "pecosis" for these areas. All cases were positive for two or more melanocytic markers and for at least one actin. S100 and desmin were focally positive in one case. Cyclin D1 was positive in 3:4 cases. Four cases of malignant PEComa are described with the existence of a unique lesion (pecosis) in one case. These tumours may manifest largely as sarcomas appearing to be undifferentiated and should be considered in their differential diagnosis.

Publication types

  • Case Reports

MeSH terms

  • Actins / analysis
  • Adult
  • Aged
  • Antigens, Neoplasm / analysis
  • Biomarkers, Tumor / analysis*
  • Cyclin D1 / analysis
  • Desmin / analysis
  • Epithelioid Cells / chemistry
  • Epithelioid Cells / pathology*
  • Epithelioid Cells / ultrastructure
  • Female
  • Humans
  • Immunohistochemistry
  • MART-1 Antigen
  • Male
  • Melanoma-Specific Antigens
  • Microphthalmia-Associated Transcription Factor / analysis
  • Microscopy, Electron
  • Middle Aged
  • Muscle, Smooth / chemistry
  • Neoplasm Proteins / analysis
  • Neoplasms, Connective and Soft Tissue / metabolism
  • Neoplasms, Connective and Soft Tissue / pathology*
  • Neoplasms, Connective and Soft Tissue / ultrastructure
  • S100 Proteins / analysis


  • Actins
  • Antigens, Neoplasm
  • Biomarkers, Tumor
  • Desmin
  • MART-1 Antigen
  • MITF protein, human
  • MLANA protein, human
  • Melanoma-Specific Antigens
  • Microphthalmia-Associated Transcription Factor
  • Neoplasm Proteins
  • S100 Proteins
  • Cyclin D1