Urinary tract cytology

Tumors of the urinary tract are relatively inaccessible to direct biopsy and are often multifocal. Since urine is easily ortained and washes over the entire mucosal surface, urine cytology is, in theory, the perfect specimen to examine to detect a tumor. Unfortunately, interpretation of urine cytology is difficult, and both false-negative and false-positive results are very well known. Diagnostic accuracy increases with the grade of the tumor. Low-grade noninvasive papillary tumors are the sources of most false-negatives. Reactive and degenerative changes due to conditions such as inflammation, stones, prostatic hyperplasia, and therapy are responsible for most false-positives. This lecture will review basic urine cytology and give some pointers to help avoid diagnostic pitfalls.