Low-Grade Papillary Urothelial Carcinoma: Understanding Your Pathology Report

Section Editor: Trevor Flood MD FRCPC
October 9, 2026

Low-grade papillary urothelial carcinoma is a type of cancer that starts from the urothelial cells that line the inside of the urinary tract. The word papillary means the tumor grows as finger-like projections that stick out from the lining. The term low grade means the tumor cells look only slightly different from normal urothelial cells under the microscope.

Low-grade papillary urothelial carcinoma most often starts in the bladder, but it can also start in the kidney or the ureters. Almost all of these tumors are non-invasive, which means the cancer cells have not grown below the lining. These tumors often recur in the bladder after treatment, but they rarely invade the bladder wall or spread to other parts of the body.

This article explains how low-grade papillary urothelial carcinoma is diagnosed and what your pathology report says about the grade, invasion, and stage of the tumor. It also explains why regular follow-up is needed.

Who gets low-grade papillary urothelial carcinoma?

Low-grade papillary urothelial carcinoma is mainly found in older adults, and most people are in their 60s or 70s when it is diagnosed. It is about four times more common in men than in women. Bladder tumors are uncommon before the age of 40, but most of those found in younger adults are low grade.

What causes low-grade papillary urothelial carcinoma?

Smoking is the most important cause of low-grade papillary urothelial carcinoma, because chemicals from tobacco smoke are filtered into the urine and damage the lining of the bladder. Long-term exposure to certain industrial chemicals, such as aromatic amines once used in dye and rubber manufacturing, also increases risk. Other causes include arsenic in drinking water and herbal products containing aristolochic acid.

A small number of urothelial carcinomas are linked to an inherited condition called Lynch syndrome. This link is strongest for tumors that start in the kidney or ureter. Stopping smoking lowers the chance of new tumors forming in the bladder after treatment.

What are the symptoms of low-grade papillary urothelial carcinoma?

The most common symptom of low-grade papillary urothelial carcinoma is blood in the urine, which is usually painless and may come and go. Because the finger-like projections are fragile, they bleed easily, even when the tumor is small. Some people notice the blood themselves, while in others it is found only on a urine test. Less common symptoms include burning during urination and needing to urinate often or urgently.

How is the diagnosis made?

The diagnosis of low-grade papillary urothelial carcinoma usually begins after blood is found in the urine. A doctor may send a urine sample for cytology, a test in which a pathologist looks for cancer cells in the urine. Low-grade tumor cells look so similar to normal cells that urine cytology is often negative, even when a tumor is present. Our article on cytology explains this test.

A urologist then looks inside the bladder with a thin camera, a procedure called cystoscopy. A low-grade papillary tumor often looks like a small piece of seaweed floating from the bladder wall. It is removed through the urethra in a procedure called a transurethral resection of bladder tumor, or TURBT. Our article on the TURBT pathology report explains the procedure and what pathologists examine.

Under the microscope, a pathologist sees thin projections called papillae, each with a central stalk of tissue and blood vessels called a fibrovascular core. In low-grade papillary urothelial carcinoma, the cells covering these papillae are mostly orderly but show small differences in size and shape. These differences separate it from noncancerous papillary growths, such as a urothelial papilloma.

The pathologist also checks whether the thick muscle layer of the bladder wall, called the muscularis propria, is present in the sample. Your TURBT report will describe the muscle layer in one of these ways:

Not identified. No muscle was included in the sample. This is common for a small, low-grade tumor because the urologist doesn’t need to remove muscle to treat it.
Present, negative for tumor. Muscle was included in the sample, and no cancer cells were seen
Present, involved by tumor. Cancer cells have grown into the muscle. This is very rare for a low-grade tumor.
Cannot be determined. The pathologist could not tell with certainty, often because the tissue was damaged during removal.

For a tumor in the kidney or ureter, a small sample is taken with a thin camera passed up through the bladder, a procedure called ureteroscopy. Imaging, such as a CT scan, often checks the kidneys and ureters for other tumors.

Histologic grade

The grade of a papillary urothelial carcinoma describes how different the tumor cells look from normal urothelial cells. For low-grade papillary urothelial carcinoma, grade is the most important finding in your report. It helps predict how the tumor will behave, and your team uses it to plan treatment and follow-up. Papillary urothelial carcinoma has two grades:

Low grade. The tumor cells look only slightly different from normal urothelial cells and are arranged in an orderly way. Low-grade tumors often come back in the bladder, but they rarely grow into the muscle or spread.
High grade. The tumor cells look very different from normal urothelial cells and are arranged disorderly. These tumors are more likely to grow into the bladder wall and are described in our article on high-grade papillary urothelial carcinoma.

Some papillary urothelial carcinomas contain a small area of high-grade cells within a mostly low-grade tumor. Under the World Health Organization (WHO) classification, 5th edition (2022), the tumor is graded as high grade when the high-grade areas make up 5% or more of the tumor. When they make up less than 5%, your report may say “low grade with less than 5% high-grade component.” These tumors seem to behave more like low-grade tumors, but your team may follow them more closely.

Some reports, especially in Europe, also assign a grade from 1 to 3 using the older 1973 WHO system. This grade is optional, and it is given alongside the low and high grade rather than replacing it. Most low-grade tumors are grade 1 or grade 2 in the older system.

Low-grade papillary urothelial carcinoma is also different from a related growth called papillary urothelial neoplasm of low malignant potential, or PUNLMP. The cells of a PUNLMP look even closer to normal, and it comes back less often. If your report says PUNLMP, it is not considered a cancer, but it is followed with cystoscopy in a similar way.

Non-invasive and invasive low-grade papillary urothelial carcinoma

After grade, the next most important finding for low-grade papillary urothelial carcinoma is whether the cancer cells have grown below the lining. This process is called invasion. Your report will name the deepest layer of the bladder wall that contains cancer cells.

Non-invasive papillary carcinoma. The cancer cells are confined to the lining and papillae, with none extending into the underlying tissue. Your report may also use the term non-invasive. This finding occurs in almost all low-grade tumors, which are staged as pTa.
Invades the lamina propria. The cancer cells have grown into the lamina propria, the thin layer of connective tissue just below the lining. This is uncommon for a low-grade tumor, and it is staged as pT1. Your team may recommend a second TURBT and closer follow-up.
Cannot be determined. The pathologist often cannot tell whether invasion is present because the tissue is damaged or poorly oriented.

Noninvasive papillary urothelial carcinoma If invasion is present, your report will also say whether lymphovascular invasion was seen. Lymphovascular invasion means cancer cells are inside a small blood vessel or lymphatic channel. It is not seen in non-invasive tumors, because the cancer cells have not reached the vessels below the lining.

Invasive papillary urothelial carcinoma

Some low-grade papillary urothelial carcinomas grow downward into the lining as smooth, rounded nests, a pattern called inverted growth. This pattern can look like invasion, but on its own it is not counted as invasion. Your report may mention inverted growth so that it is not confused with a more serious finding.

Your report may also note whether urothelial carcinoma in situ was found in the nearby lining. This flat form of the cancer is always high grade. It is uncommon alongside a low-grade tumor, but when it is present, your team will treat the cancer as high risk.

Margins

A TURBT removes low-grade papillary urothelial carcinoma in many small pieces, so the pathologist cannot tell which edges were cut during surgery. For this reason, pathologists do not report margins on a TURBT specimen. Whether any tumor remains is judged by the urologist during the procedure and by follow-up cystoscopy.

Biomarker and molecular testing

Biomarker testing for low-grade papillary urothelial carcinoma looks for features of the tumor cells that can guide treatment or point to an inherited condition. These tests are not part of most reports for low-grade tumors. They are mainly done for tumors in the kidney or ureter, if the cancer becomes advanced, or if a clinical trial is being considered.

FGFR3

FGFR3 is a gene that makes a protein involved in cell growth. Changes in FGFR3 are found in most low-grade non-invasive papillary urothelial carcinomas, more often than in any other type of bladder cancer. Testing is done with a molecular test such as next-generation sequencing (NGS). The test looks for a mutation or a fusion with another gene.

Detected. An FGFR3 change was found. Researchers are studying drugs that block FGFR3 and are delivered directly to the bladder in clinical trials for low-grade tumors. If the cancer ever becomes advanced, the FDA approved erdafitinib in January 2024 for advanced urothelial carcinoma with certain FGFR3 changes.
Not detected. No FGFR3 change was found. This does not change the standard treatment of a low-grade tumor.

Mismatch repair proteins

Mismatch repair proteins fix mistakes that happen when a cell copies its DNA. Testing looks for four proteins called MLH1, PMS2, MSH2, and MSH6. For low-grade papillary urothelial carcinoma, it is done most often on tumors from the kidney or ureter, because of their link to Lynch syndrome.

Intact, retained, or no loss of expression. All four proteins are present. This is the normal result, and it makes Lynch syndrome unlikely.
Loss of expression. One or more proteins are missing. This result does not confirm Lynch syndrome, but it leads to a referral for genetic counseling and a blood test.

We test other biomarkers, such as HER2 and PD-L1, only if the cancer becomes advanced. We describe them in our article on invasive urothelial carcinoma. For more information on tumor testing, visit our Biomarkers and Genetic Testing section.

Pathologic stage (pTNM)

We assign the pathologic stage for low-grade papillary urothelial carcinoma of the bladder using the TNM system from the AJCC Cancer Staging Manual, 8th edition. The tumor stage (pT) describes how deeply the cancer has grown. Spread to lymph nodes (N) and distant organs (M) is very rare for low-grade tumors.

Tumor stage (pT)

pTa. The tumor is non-invasive papillary carcinoma. This stage occurs in almost all low-grade papillary urothelial carcinomas.
pT1. The tumor has grown into the lamina propria but not into the muscle layer. This is uncommon for a low-grade tumor.
pT2 or higher. The tumor has grown into the muscle layer or beyond. This is very rare for a low-grade tumor and is described in our article on invasive urothelial carcinoma.

Nodal stage (pN)

Lymph nodes are not removed during a TURBT, so reports for low-grade papillary urothelial carcinoma usually do not include a nodal stage. Your report may say that the nodal stage cannot be assessed, which is expected. Tumors that start in the kidney or ureter are staged slightly differently because the wall of these organs is thinner.

What is the prognosis?

The prognosis for low-grade papillary urothelial carcinoma is very good, and very few people die from this cancer. The main challenge is that new tumors often appear in the bladder after treatment. This is why regular cystoscopy is part of the care for this cancer.

Survival. About 98 in 100 people with non-invasive bladder cancer are alive five years after diagnosis, and about 2 in 100 are not.
Coming back. About half of people have a new tumor in the bladder within five years, and some have several over their lifetime. Most new tumors are low-grade and non-invasive.
Becoming more serious. Between about 3 and 19 in 100 people have a later tumor that is high grade or invasive. About 2 in 100 develop cancer that grows into the muscle, rising to about 8 in 100 for those with several risk factors.

These numbers are averages for large groups of people and don’t predict what will happen to you. Features that are linked to a higher chance of the tumor coming back include:

Several tumors. More than one tumor seen at cystoscopy.
A large tumor. A tumor larger than 3 cm.
Early return. A new tumor within one year of the first.
Frequent return. More than one new tumor each year.
Return despite treatment. A new tumor after medicine was placed in the bladder.

Some findings in your report are linked to a higher chance of the cancer becoming more serious. These include a small high-grade component, invasion of the lamina propria, and carcinoma in situ in the nearby lining.

What happens after the diagnosis?

After a diagnosis of low-grade papillary urothelial carcinoma, your urologist combines the grade and invasion in your report with the number and size of the tumors. Together, these findings place the cancer in a low-risk or intermediate-risk group. This group guides treatment and how often you will need cystoscopy.

TURBT. For most people, the TURBT itself removes the low-grade tumor completely.
A single dose of medicine in the bladder. A chemotherapy drug such as gemcitabine or mitomycin may be placed in the bladder soon after the TURBT. This lowers the chance of a new tumor by about one third.
A course of medicine in the bladder. For intermediate-risk tumors, a course of weekly chemotherapy, or sometimes BCG, may be given to lower the chance of new tumors.
Treatment without surgery. In June 2025, the FDA approved a form of mitomycin placed in the bladder for some people whose low-grade tumors keep coming back. In the study that led to approval, about 78 in 100 people had no visible tumor three months after treatment.
Watching small tumors. For some people with small low-grade tumors that come back, the urologist may watch them with cystoscopy, or treat them in the office with heat, instead of repeat surgery.
Tumors in the kidney or ureter. Low-grade tumors in these sites can often be treated through a scope, which preserves the kidney. In April 2020, the FDA approved a mitomycin gel placed into the kidney for low-grade tumors of the upper urinary tract.

Approval and access to these drugs differ by country, and your care team can explain what applies where you live. Follow-up for low-grade papillary urothelial carcinoma usually begins with a cystoscopy about three months after the TURBT. If no new tumor is found, cystoscopy is then done less often over the following years.

Questions to ask your doctor

Is my tumor low grade throughout, or does it have a small high-grade component?
Is the tumor non-invasive, or has it grown into the lamina propria?
Was muscle included in my TURBT sample, and does that matter for my tumor?
Was carcinoma in situ found in the lining nearby?
How many tumors were there, and how large was the biggest one?
Is my cancer low risk or intermediate risk?
Will I receive a dose of medicine in my bladder after the TURBT?
Do I need a course of treatment in the bladder?
If a small tumor comes back, could you watch it or treat it without surgery?
Should my kidneys and ureters be checked for other tumors?
How often will I need cystoscopy, and for how long?
What symptoms should make me call you before my next cystoscopy?