Transitional epithelial cells originate from the renal pelvis, ureters, urinary bladder and/or
urethra. Their size and shape depends on the depth of origin in the mucosa. Most often they
are round or polygonal; less commonly pear-shaped, tailed, or spindle-shaped. They are
generally somewhat smaller and smoother in outline than squamous cells, but larger than
WBC. They may develop refractile, fatty inclusions as they degenerate in older specimens
(arrow, upper panel).
In cleanly-collected normal samples, transitional cells are few, and present as single cells or small clusters (arrow, lower panel, Sedi-Stain). Specimens collected by catheter sometimes contain large sheets of cells scraped off during passage of the catheter. In inflammatory conditions causing hyperplasia of the urinary mucosa, larger numbers/clusters may exfoliate. In such cases, differentiation from neoplastic transitional cells may be difficult. |
Last Updated: January 16, 1996