title: Transformed mesothelial cells in patients on CAPD for medium- to long-term periods.
abstract: OBJECTIVE
  To describe the characteristics of abnormal cells present in the peritoneal effluent of 4 continuous ambulatory peritoneal dialysis (CAPD) patients; the cells were accidentally detected in a longitudinal study of cell populations in 83 patients.
  
  
  METHODS
  Descriptive study.
  
  
  METHODS
  Four stable CAPD patients (2 male, 2 female).
  
  
  METHODS
  Peritoneal cells were collected from nocturnal peritoneal effluent (NPE) by centrifugation.
  
  
  METHODS
  Light microscopy, ultrastructural, cytochemical, and immunohistochemical characteristics were studied.
  
  
  RESULTS
  The abnormal cells were characterized by a flat appearance, large size (diameter 100 microns)--six to ten times larger than a normal macrophage, a broad acidophilic cytoplasm with rare granulations, and a low nucleus/cytoplasm ratio. The nucleus was pyknotic, with dense chromatin and sometimes appeared fragmented. Its number presented a considerable variability between the patients and was much higher in the 2 females. This number remained stable in each patient over time. These cells were negative for beta-glucuronidase and positive for PAS stain with variable intensity. A very low number of flat cells were positive for vimentin with weak intensity, whereas cytokeratin and epithelial membrane antigen (EMA) were positive in a higher number of cells with medium to strong intensity. Ultrastructural studies showed numerous short surface microvilli, cytoplasm well-developed with intracytoplasmic lumina and abundant, dispersed intermediate filaments, scattered mitochondria, and stacks of rough endoplasmic reticulum were observed. Dispersed secretory vacuoles and isolated lipid vacuoles were present.
  
  
  CONCLUSIONS
  All these features imply that they are mesothelial in origin and are suggestive of a change known as peritoneal squamous metaplasia. To date, the clinical follow-up of our patients has shown a benign outcome; further studies are necessary to elucidate the significance of this peritoneal squamous metaplasia in CAPD patients.
authors.affiliation: Nephrology, Hospital La Paz, Madrid, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Selgas
authors.forename: M
authors.initials: M
authors.lastname: Fernandez de Castro
authors.forename: J M
authors.initials: JM
authors.lastname: Viguer
authors.forename: E
authors.initials: E
authors.lastname: Burgos
authors.forename: M A
authors.initials: MA
authors.lastname: Bajo
authors.forename: C
authors.initials: C
authors.lastname: Carcamo
authors.forename: F
authors.initials: F
authors.lastname: Vara
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002467:Cell Nucleus / Q000648:ultrastructure; D048429:Cell Size; D003593:Cytoplasm / Q000648:ultrastructure; D004721:Endoplasmic Reticulum / Q000648:ultrastructure; D004848:Epithelium / Q000473:pathology / Q000648:ultrastructure; D005260:Female; D005966:Glucuronidase / Q000032:analysis; D006801:Humans; D007382:Intermediate Filaments / Q000648:ultrastructure; D007633:Keratins / Q000032:analysis; D008137:Longitudinal Studies; D008297:Male; D008871:Microvilli / Q000648:ultrastructure; D008875:Middle Aged; D008928:Mitochondria / Q000648:ultrastructure; D018396:Mucin-1 / Q000032:analysis; D009363:Neoplasm Proteins / Q000032:analysis; D010531:Peritoneal Dialysis, Continuous Ambulatory; D010537:Peritoneum / Q000473:pathology* / Q000648:ultrastructure; D012737:Sex Factors; D013997:Time Factors; D014617:Vacuoles / Q000648:ultrastructure; D014746:Vimentin / Q000032:analysis
chemical_list: D018396:Mucin-1; D009363:Neoplasm Proteins; D014746:Vimentin; D007633:Keratins; D005966:Glucuronidase