Nephrogenic Adenoma of the Urinary Bladder: A Review of the Literature

Background . Nephrogenic adenoma of the urinary bladder (NAUB) is a rare lesion associated with nonspecific symptoms and could inadvertently be misdiagnosed. Aim . To review the literature. Methods . Various internet search engines were used. Results . NAUB is a benign tubular and papillary lesion of the bladder, is more common in men and adults, and has been associated with chronic inflammation/irritation, previous bladder surgery, diverticula, renal transplantation, and intravesical BCG; recurrences and malignant transformations have been reported. Differential diagnoses include clear cell adenocarcinoma, endocervicosis, papillary urothelial carcinoma, prostatic adenocarcinoma of bladder, and nested variant of urothelial carcinoma; most NAUBs have both surface papillary and submucosal tubular components; both the papillae and tubules tend to be lined by a single layer of mitotically inactive bland cells which have pale to clear cytoplasm. Diagnosis may be established by using immunohistochemistry (positive staining with racemase; PAX2; keratins stain positive with fibromyxoid variant), electron microscopy, DNA analysis, and cytological studies. Treatment . Endoscopic resection is the treatment but recurrences including sporadic malignant transformation have been reported. Conclusions . There is no consensus on best treatment. A multicentre study is required to identify the treatment that would reduce the recurrence rate, taking into consideration that intravesical BCG is associated with NAUB.