title: HMB-45 negative angiomyolipoma of the orbit: a case report and review of the literature.
abstract: BACKGROUND
  Angiomyolipoma is a benign mesenchymal tumor composed of variable amounts of smooth muscle, adipose tissue and thick-walled blood vessels, and usually named PEComas (perivascular epithelioid cell tumors). PEComas share overlapping histopathological features with epithelioid cells along a perivascular distribution and characteristic immunohistochemistry with coexpression of myoid and melanocytic markers (HMB-45 /or Melan-A). We report the first case of primary orbital angiomyolipoma with negative melanocytic marker.
  
  
  METHODS
  An 80-year-old Asian woman had a 2-year history of progressive swelling in the left upper eyelid. External examination revealed 3 cm of relative proptosis of the left eye and a palpable mass in the left superonasal orbit. Computed tomographic scan demonstrated a circumscribed, heterogeneous orbital mass. Excision biopsy was done and the histological finding demonstrated the orbital mass was composed of mature adipocytes, intermingled with spindle or oval-shaped cells, and accompanied by thick-walled blood vessels. Immunohistochemically, tumor cells were positive for CD34 and HHF-35, but negative for cytokeratin, HMB-45 and Melan-A. The diagnosis of angiomyolipoma was made. No recurrence was noted at 2-year follow-up.
  
  
  CONCLUSIONS
  In our case, the HMB-45 negativity may be explained by the rarity of the epithelioid cells, and the HMB-45 positivity is often weaker or absent in spindle cells. Angiomyolipoma, although rare, should be added to the differential diagnosis of space-occupying orbital lesion.
authors.affiliation: Department of Ophthalmology, Taipei Veterans General Hospital, No. 201, Sec.2, Shih-Pai Road, Taipei, 11217, Taiwan, R.O.C.|Department of Ophthalmology, School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Che-Yu
authors.initials: CY
authors.lastname: Lin
authors.affiliation: Department of Ophthalmology, Taipei Veterans General Hospital, No. 201, Sec.2, Shih-Pai Road, Taipei, 11217, Taiwan, R.O.C.. cctsai1234@yahoo.com.|Department of Ophthalmology, School of Medicine, National Yang-Ming University, Taipei, Taiwan. cctsai1234@yahoo.com.
authors.forename: Chieh-Chih
authors.initials: CC
authors.lastname: Tsai
authors.affiliation: Department of Ophthalmology, School of Medicine, National Yang-Ming University, Taipei, Taiwan.|Department of Ophthalmology, Koo Foundation Sun Yat-Sen Cancer Center, Taipei, 112, Taiwan.
authors.forename: Hui-Chuan
authors.initials: HC
authors.lastname: Kau
authors.affiliation: Department of Ophthalmology, Taipei Veterans General Hospital, No. 201, Sec.2, Shih-Pai Road, Taipei, 11217, Taiwan, R.O.C.|Department of Ophthalmology, School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Wei-Kuang
authors.initials: WK
authors.lastname: Yu
authors.affiliation: Department of Ophthalmology, Taipei Veterans General Hospital, No. 201, Sec.2, Shih-Pai Road, Taipei, 11217, Taiwan, R.O.C.|Department of Ophthalmology, School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Shu-Ching
authors.initials: SC
authors.lastname: Kao
authors.affiliation: Department of Ophthalmology, Taipei Veterans General Hospital, No. 201, Sec.2, Shih-Pai Road, Taipei, 11217, Taiwan, R.O.C.|Department of Ophthalmology, School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Catherine Jui-Ling
authors.initials: CJ
authors.lastname: Liu
mesh_terms: D000369:Aged, 80 and over; D018207:Angiomyolipoma / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology; D018952:Antigens, CD34 / Q000378:metabolism; D014408:Biomarkers, Tumor / Q000378:metabolism*; D001706:Biopsy; D006801:Humans; D007150:Immunohistochemistry; D058965:MART-1 Antigen / Q000378:metabolism; D058950:Melanoma-Specific Antigens / Q000378:metabolism*; D009918:Orbital Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology; D014057:Tomography, X-Ray Computed; D058951:gp100 Melanoma Antigen
chemical_list: D018952:Antigens, CD34; D014408:Biomarkers, Tumor; D058965:MART-1 Antigen; C548667:MLANA protein, human; D058950:Melanoma-Specific Antigens; C548637:PMEL protein, human; D058951:gp100 Melanoma Antigen