Urothelial cells

October 17, 2023

Urothelial cells, also known as transitional cells, line the urinary tract, which includes the bladder, ureters, urethra, and part of the kidney. These cells form a specialized barrier called the urothelium that prevents urine from penetrating the underlying tissues. They can also expand and contract based on the volume of urine present, which reflects their transitional nature.

Microscopic features

Under the microscope, urothelial cells are organized in multiple layers and display a distinct morphology suitable for their role in lining the urinary tract. Specifically, the cells at the surface of the urothelium appear large and dome-shaped, often showing a slightly irregular, polygonal outline. Pathologists often refer to these cells as umbrella cells. Urothelial cells also tend to have a central, round to oval-shaped nucleus that is relatively large and sometimes features a prominent nucleolus with finely distributed chromatin, giving it a somewhat clear appearance. The cytoplasm varies from lightly to moderately eosinophilic (pinkish under a stain) and is abundant, reflecting their protective function. This layering and cellular structure enables the urothelium to stretch and adjust to changes in urine volume, maintaining an effective barrier against urine and potential pathogens.

Is it normal for urothelial cells to be found in urine?

Yes, it is normal for urothelial cells to be found in urine. This can be seen when a urine sample is examined under the microscope.

What does it mean if urothelial cells are described as atypical?

Pathologists use the word atypical to describe cells that look abnormal when examined under the microscope. Cells can be described as atypical based on their shape, size, or colour. Atypical urothelial cells can be seen in cancer but can also be seen in other conditions, such as bladder infections.

What types of cancers start from urothelial cells?

Types of cancer that start from urothelial cells include urothelial carcinoma, papillary urothelial carcinoma, and urothelial carcinoma in situ.

About this article

Doctors wrote this article to help you read and understand your pathology report. Contact us if you have questions about this article or your pathology report.

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