Large flat polygonal cells with "hard" (dense) cytoplasm; usually stain pink on a pap smear (image A).
Nuclei should be round with smooth borders and finely distributed chromatin.
N:C ratio should be very low (small nucleus, lots of cytoplasm) – generally <1:2 (image B).
Increased numbers may be seen in normal urine.
As a contaminant from the distal urethra, vagina, or vulva.
In cases of squamous metaplasia, usually of the bladder trigone (seen in 40% of females and in men undergoing estrogen therapy for prostate cancer).
In cases of chronic irritation and inflammation.