TRANSFORMED MESOTHELIAL CELLS IN PATIENTS ON CAPD FOR MEDIUM TO LONG TERM PERIODS

.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. .Design: Descriptive study. .Participants: Four stable CAPD patients (2 male, 2 female). .Interventions: Peritoneal cells were collected from nocturnal peritoneal effluent (NPE) by centrifugation. .Measurements: Light microscopy, ultrastructural, cytochemical, and immunohistochemical characteristics were studied. .Results: The abnormal cells were characterized bya flat appearance, large size (diameter 100 μm) -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 betaglucuronidase 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.