Nephrogenic adenoma identified on urine cytology using PAX-2 immunostaining

Urine cytology is a sensitive and specific method in detecting urothelial carcinoma of the urinary bladder, particularly the high-grade ones. However, the cytologic features of nonneoplastic lesions of the lower urinary tract, including nephrogenic adenoma, are nonspecific and may cause false positive diagnosis. Recent evidence has demonstrated that nephrogenic adenoma is a true "nephrogenic" lesion derived from the exfoliated and implanted renal tubular cells in the urinary tract. This has promoted the use of immunostaining of renal transcription factor PAX2 in tissue biopsies to differentiate nephrogenic adenoma from the common malignant tumors of the lower urinary tract. We report here that PAX2 immunostaining can also be used in urine cytology specimen to identify nephrogenic adenoma. Combination of PAX2 immunostaining and cytologic analysis may increase the accuracy in identifying this benign lesion in urine cytology specimen and therefore reduce unnecessary repeat cystoscopy and biopsy procedures. This may be a cost effective follow- up method for patients with an established diagnosis of nephrogenic adenoma.