Practical Matters: Difficulties in diagnosing transitional cell carcinoma
A urinalysis may reveal abnormal epithelial cells, but in the face of inflammation, transitional cells may be reactive, and distinguishing reactive cells from neoplastic cells can be difficult, even for an experienced clinical pathologist. While many clinicians use the veterinary bladder tumor antigen (V-BTA—Polymedco) urine test to confirm transitional cell carcinoma, false positive results may occur when pyuria (> 30 WBC/HPF), hematuria (> 30 RBC/HPF), proteinuria (4+), or glucosuria (4+) is present. Since this test has an overall sensitivity of 90% and an overall specificity of 78% for diagnosing transitional cell carcinoma, it may be more useful in routine screenings of at-risk populations (e.g. Scottish terriers, West Highland white terriers, Shetland sheepdogs, beagles, geriatric patients) in the absence of urinary tract signs.
An ultrasonographic examination of the urinary tract may reveal a mass in the trigone or adjacent urethra, providing suggestive, but not definitive, evidence of transitional cell carcinoma.Although somewhat controversial, I do not perform ultrasound-guided fine-needle aspiration biopsy in patients with suspected transitional cell carcinoma because of concerns about seeding the needle tract with neoplastic cells. Transitional cell carcinoma is thought to be easily transplantable, so samples should be obtained by way of the urinary tract. I prefer to use either traumatic catheterization or cystoscopy-guided biopsy to obtain diagnostic samples. While samples obtained via cystoscopy are small, there is a classic gross appearance (friable, white fimbriated tissue), which can provide further indirect support for the histologic diagnosis.
Linda Fineman, DVM, DACVIM (oncology)