Ciliated Cells in Renal Calyx mucosa: Metaplastic Change or Developmental Abnormality? Immunohistochemical Study of one Case and Review of the Literature

Ciliated epithelial cells have been rarely observed in urothelium lined mucosa. Only extremely rare reports in the literature have described this phenomenon and no cases have been described in other sites than the male urethra. Herein, we illustrate the finding of ciliated pseudostratified columnar cells in the renal calyx mucosa adjacent to an area of urothelial invasive carcinoma in an 82 year-old man with previous history of nephrolithiasis. The ciliated cells covered a linear extension of 0.5 cm: they were positive for keratin 7 and keratin 8/18 and negative for keratin 20. Alcian blue staining was positive in some vacuoles in the apical cytoplasm of the same cells whereas PAS (Periodic Acid-Schiff) staining was negative. GATA3 resulted negative in ciliated cells except for a layer in the basal portion of the epithelium, just above the basal membrane. The actual prevalence of ciliated epithelia in the urinary tract is not well documented and the current knowledge on the subject is limited to electron scanning microscopy studies. The significance of this phenomenon remains unknown: it could be either a developmental abnormality or more probably a metaplastic change. Associated urolithiasis, which has been described in both a previous report and in the present one, could hypothetically represent a possible trigger for this unusual cell change. However, this hypothesis needs to be confirmed through further investigation.