Atypical (neoplastic) cells in urine sediment in cats and dogs
This line appears when the person reading the urine sediment sees epithelial cells that look abnormal — different sizes, large or multiple nucleoli — the kind of cells that a tumour of the urinary tract can shed. In dogs the main concern is urothelial carcinoma (transitional cell carcinoma) of the bladder or urethra. It is a reason to look further, not a diagnosis: inflamed lining can look atypical too, and the final answer usually comes from other tests.
What it shows
The bladder, ureters, renal pelvis and the first part of the urethra are lined by transitional epithelium. Tumours of the urinary and genital tract may shed their own cells. In dogs the most common such tumour is transitional cell (urothelial) carcinoma of the bladder, urethra or prostatic urethra; lymphoma and kidney carcinoma shed cells into urine only rarely.
Cells are called atypical when they show features of malignancy: marked variation in the size of cells and nuclei, several nucleoli of different sizes, cells with more than one nucleus, very large nucleoli. These features can be judged reliably only on a stained smear of the sediment; in an unstained preparation they are hard to see, and normal transitional cells are difficult to tell from tumour cells.
Higher than reference — what it may be a sign of
- Urothelial carcinoma — the main suspicion in a dog. It often arises at the neck of the bladder (trigone) or in the urethra; in males it often involves the prostate. Blood in the urine is common with it.
- Prostate carcinoma in male dogs, and rarely lymphoma or kidney carcinoma.
- Inflammation that only looks like a tumour. Urothelial carcinoma often comes together with a urinary infection, and inflamed lining sheds more cells, as it does after catheterisation; they are hard to tell from tumour cells. Urine cytology can give both false-positive and false-negative results, so a single finding is read with caution.
The vet decides how to check: imaging (usually ultrasound), a urine test for the BRAF gene mutation, tissue examination. A positive BRAF test in urine is regarded as diagnostic because of its high specificity; in one study on voided urine it found 85% of dogs with urothelial or prostate carcinoma, with no false positives. Not every tumour carries the mutation, and it has occasionally been found in non-tumour changes of the lining. When the test is negative, a biopsy is needed for a definitive diagnosis.
Lower than reference
“Not seen” is the usual result, but it does not rule out a tumour: tumours do not always shed cells into urine. Stored urine is harder to read — cells and nuclei swell over time and malignant features blur — so a fresh sample is better.
Look at together with
- Epithelial cells in sediment — how many transitional cells are shed overall, and whether a catheter could explain them.
- Red and white cells in sediment — blood is common with bladder tumours; many white cells point to inflammation.
- Bacteria in urine and culture — the signs of a bladder tumour resemble an infection, and secondary infection is common.
- Blood on the dipstick — a quick screen for bleeding into urine.
Units and conversion
There are no units: this is a description, not a count. Epithelial cells in sediment are graded at low magnification as none seen, few, moderate or many; for atypical cells the lab usually writes in words whether they were seen and what the stained smear showed. In the app the result is stored as text, as written on the form.
Reference range
The reference range is on your lab’s form. There is no number to compare against. In a healthy animal atypical cells are not expected; a few ordinary transitional cells are normal.
Cats and dogs
Tumours of the lower urinary tract are rare in cats. When they occur, transitional cell carcinoma is still the most frequently diagnosed primary malignant one, but in cats it sits at the bladder neck less often than in dogs — in about a quarter of cats in a large multi-centre study. Lymphoma can occasionally shed cells into urine: in one cat with kidney lymphoma the tumour cells in the sediment gave the diagnosis. The BRAF data above come from dogs.
Bladder tumours are more common in dogs. Scottish Terriers carry a much higher risk than mixed breeds, and female dogs are also at higher risk. Because a needle passed through the bladder wall may, rarely, spread tumour cells, urine for this question is usually collected by voiding or catheter. The BRAF urine test has been developed for dogs.
Add a lab form — Pet Tracker Space recognises the lines, keeps the form’s units and draws each indicator over time with your lab’s reference band.
Sources
- eClinPath (Cornell University College of Veterinary Medicine). Urinalysis — Cellular constituents.
- eClinPath (Cornell University College of Veterinary Medicine). Urinalysis — Cell quick guide.
- Merck Veterinary Manual, professional version. Neoplasia of the Urinary System in Dogs and Cats.
- Veterinary Sciences (MDPI), 2018. Lower Urinary Tract Neoplasia.
- Animals (MDPI), 2024. Diagnostic Value of Conventional PCR for Detecting BRAF V595E Mutation in Liquid and Tissue Specimens of Canine Urothelial and Prostate Carcinomas.
This page explains what a lab value means. It is not a diagnosis and not a substitute for your veterinarian — only they can interpret results for your pet.