6Ĭells from the convoluted tubular epithelium are the largest cells in the nephron, present at the entrance to Bowman capsule and extending to the beginning of the loop of Henle. In such cases, these features should be reported in the diagnosis because the presence of such “ghost” cells may be of considerable significance, representing leukoplakia or squamous cell carcinoma of the bladder. Squamous cells may also be anucleate and fully keratinized. Such cells may be observed during pregnancy and in early menopause, and sometimes they are noted in women or men receiving hormonal therapy (androgen deprivation therapy for prostate cancer). Navicular cells are intermediate squamous cells with abundant cytoplasmic glycogen content and peripheral nuclei these cells stain yellow with Papanicolaou stain. Among the benign squamous cells, one may see superficial cells, intermediate cells, and smaller parabasal cells. In men, the origin of the squamous cells is the terminal portion of the urethra or, in rare cases, a vaginal type of squamous metaplasia. Voided urine sediment may also contain squamous cells derived from the vulva, vagina, or uterine cervix. 7 In women, these cells originate in the urethral squamous epithelium and in the trigone of the urinary bladder, and they are usually glycogenated. Such cells are more abundant in female than male patients. Squamous cells of varying size and degrees of maturation are common in urine sediment, particularly in voided specimens (Fig. In voided urine, the nuclei may be pale or opaque and occasionally somewhat darker. They are usually finely granular and benign appearing, with one or rarely two small chromocenters. 7 The nuclei of the smaller urothelial cells are approximately the same size, measuring approximately 5 µm in diameter ( Fig. These cells are often spherical or round, particularly in voided urine, but they may also show cytoplasmic extensions. Single cells resemble parabasal squamous cells in size and configuration. The amount of basophilic cytoplasm in such cells depends on the layer of origin, and this cytoplasm is more abundant in cells derived from superficial layers. These cells are polygonal or elongate, sometimes columnar, and almost always display cytoplasmic extensions in contact with other cells. 18, 19 When the deep cells are removed by an instrument, they often appear in loose clusters. Such clusters are often misinterpreted as low-grade papillary carcinoma. Clusters of urothelial cells may be tightly packed and assume spherical “pseudopapillary” configurations with sharp borders. Single small urothelial cells are observed in voided urine. Cells originating from the deeper layers of the urotheliumĮpithelial cells smaller than the superficial cells that are derived from the deeper layers of the urothelium often exfoliate in clusters, particularly if the specimen was obtained with an instrument.

Tissue fragments in urine