Urothelial carcinoma in situ (CIS)

by Jason Wasserman MD PhD FRCPC and Zuzanna Gorski MD
January 5, 2024

Urothelial carcinoma in situ (CIS) is a type of non-invasive cancer. It can occur anywhere along the urinary tract which includes the bladder, ureters, urethra, and kidneys. If left untreated, urothelial carcinoma in situ can evolve into a type of invasive cancer called urothelial carcinoma.

This article will help you understand your diagnosis and your pathology report for urothelial carcinoma in situ.

The urinary tract

The urinary tract is a system designed to help remove waste and excess water from the body through the production of urine. The urinary tract includes the kidneys, ureters, bladder, and urethra. Urine made in the kidneys flows into the bladder by way of the ureters. The bladder stores the urine until it is released from the body by way of the urethra. The inside surface of the entire urinary tract is lined by specialized urothelial cells that form a barrier called the urothelium.


What are the symptoms of urothelial carcinoma in situ?

Symptoms associated with urothelial CIS include blood in the urine, pain when urinating, and the need to urinate more frequently or with greater urgency. For some patients, urothelial CIS does not produce any symptoms and the disease is found incidentally (by accident) when tests are performed for another reason.

What causes urothelial carcinoma in situ?

Studies have shown that a wide variety of toxins, medications, and infections are associated with an increased risk of developing urothelial CIS. Toxins that can cause urothelial CIS include tobacco smoke, opium, benzidine-based dyes, aromatic amines, arsenic, and aristolochic acid produced by Aristolochia plants (which are commonly used in herbal medications). Chronic (long-term) inflammation in the bladder caused by infections such as the Schistosoma haematobium, prolonged indwelling catheter use, and some medical treatments including radiation to the pelvis and chemotherapy with chlornaphazine or cyclophosphamide have also been shown to increase the risk of developing urothelial CIS in the bladder.

Why is urothelial carcinoma in situ called non-invasive?

Urothelial carcinoma in situ is called “non-invasive” because the tumour cells are found entirely within a thin layer of tissue called the urothelium. Non-invasive tumour cells are unable to spread to other parts of the body.

Urothelial carcinoma in situ

Microscopic features of urothelial carcinoma in situ

In urothelial carcinoma in situ, abnormal urothelial cells are seen throughout the urothelium, a thin layer of tissue that covers the inside of the urinary tract. The tumour cells are usually larger than normal urothelial cells and the nuclei are hyperchromatic (darker). Pathologists often use the terms atypia or atypical to describe these abnormal tumour cells. Mitotic figures (cells dividing to create new tumour cells) are also usually seen and some may be described as atypical mitotic figures because they are dividing abnormally.

urothelial carcinoma in situ
This is a real picture of urothelial carcinoma in situ viewed under the microscope.

What stage is urothelial carcinoma in situ?

When urothelial carcinoma in situ occurs on its own, it is given the pathologic tumour stage Tis which stands for “in situ” or “non-invasive” disease. When this condition is found along with invasive cancer such as urothelial carcinoma, the final tumour stage depends on how far the tumour cells in the urothelial carcinoma have spread into the tissues below the urothelium.

About this article

This article was written by doctors to help you read and understand your pathology report. Contact us if you have any questions about this article or your pathology report. Read this article for a more general introduction to the parts of a typical pathology report.

Other helpful resources

Atlas of Pathology
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