title: [Perivascular epithelioid cell tumor of urinary system: a clinicopathologic analysis of 21 cases].
abstract: OBJECTIVE
  To study the clinicopathologic features and differential diagnosis of perivascular epithelioid cell tumors (PEComas) occurring in the urinary system.
  
  
  METHODS
  The clinicopathologic features of 21 cases of PEComa from September 2002 to September 2010 occurring in the urinary system were retrospectively reviewed. Immunohistochemical study for HMB 45, S-100 protein, smooth muscle actin, desmin, Melan A and Ki-67 was carried out.
  
  
  RESULTS
  Amongst the 21 cases studied, there were 5 males and 16 females. The age of patients ranged from 16 to 76 years (median = 51.3 years). Twenty cases occurred in the kidney and 1 in the bladder. The predominant histopathologic subtype of renal PEComas was classic type (10/20), followed by epithelioid type (5/20), smooth muscle type (3/20), inflammatory type (1/20) and sclerosing type (1/20). Immunohistochemical study showed that HMB 45 and smooth muscle actin were positive in 95.2% (20/21) and 80.9% (17/21) cases, respectively. Melan A, desmin and S-100 protein were expressed in 71.4% (15/21), 61.9% (13/21) and 33.3% (7/21) cases, respectively. The mean proliferative index was 1.29% (range = 0 to 5%). HMB 45 and Melan A were expressed in all of the 5 cases of epithelioid PEComas, whereas smooth muscle actin and desmin were only expressed in one of them. There was no significant difference between epithelioid PEComas and non-epithelioid PEComas in the expression of HMB 45, Melan A, smooth muscle actin and desmin. Positive staining for HMB 45 and smooth muscle actin was demonstrated in the case of bladder PEComa.
  
  
  CONCLUSIONS
  PEComas of the urinary system predominantly affect the kidney. Epithelioid renal PEComas and bladder PEComa are relatively rare and have unique pathologic features. It is necessary to distinguish PEComas from other malignant tumors. Immunohistochemical study for HMB 45, Melan A and smooth muscle actin is helpful for confirmation of diagnosis.
authors.affiliation: Department of Pathology, Peking University People's Hospital, Beijing, China.
authors.forename: Gong-wei
authors.initials: GW
authors.lastname: Wang
authors.forename: Ying
authors.initials: Y
authors.lastname: Wang
authors.forename: Yun-xin
authors.initials: YX
authors.lastname: Chen
authors.forename: Qing
authors.initials: Q
authors.lastname: Li
authors.forename: Dan-hua
authors.initials: DH
authors.lastname: Shen
mesh_terms: D000199:Actins / Q000378:metabolism*; D000293:Adolescent; D000328:Adult; D000368:Aged; D002292:Carcinoma, Renal Cell / Q000378:metabolism / Q000473:pathology; D003893:Desmin / Q000378:metabolism; D003937:Diagnosis, Differential; D005260:Female; D046152:Gastrointestinal Stromal Tumors / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D007680:Kidney Neoplasms / Q000378:metabolism / Q000473:pathology*; D007890:Leiomyosarcoma / Q000378:metabolism / Q000473:pathology; D058965:MART-1 Antigen / Q000378:metabolism*; D008297:Male; D008545:Melanoma / Q000378:metabolism / Q000473:pathology; D058950:Melanoma-Specific Antigens / Q000378:metabolism*; D008875:Middle Aged; D054973:Perivascular Epithelioid Cell Neoplasms / Q000378:metabolism / Q000473:pathology*; D009418:S100 Proteins / Q000378:metabolism; D001749:Urinary Bladder Neoplasms / Q000378:metabolism / Q000473:pathology; D055815:Young Adult; D058951:gp100 Melanoma Antigen
chemical_list: C541116:ACTA2 protein, human; D000199:Actins; D003893:Desmin; D058965:MART-1 Antigen; D058950:Melanoma-Specific Antigens; C548637:PMEL protein, human; D009418:S100 Proteins; D058951:gp100 Melanoma Antigen