INVERTED PAPILLOMA OF THE KIDNEY: A SYSTEMATIC REVIEW OF LITERATURE

Introduction: Inverted Papilloma (IP) of the bladder is an infrequent event (2.2% of all cancers of the bladder) (Picozzi, Urol Oncol 2012). The IP of the upper urinary tract and in particular of the renal pelvis is exceptionally rare. We performed a systematic review of the literature on this unusual pathological findings. Materials and Methods: We carried out a systematic research from January 1974 to January 2013 on the Medline, Embase and Cochrane Library using the key words: “renal inverted papilloma”, “inverted papilloma of the upper urinary tract” “inverted papilloma kidney”, restricted to English articles. Results: We identify 39 articles in literature and 14 are included in this review, for a total of 19 clinical cases. The mean age of presentation of renal IP was 65.1 years (range 49 to 89), with a male/female ratio of 18/1. In 1 case (5.3%) the clinical presentation of the IP is synchronous with a carcinoma of the bladder (3) and in another case with an urothelial neoplasm on the controlateral kidney (2). The finding of IP in the kidney was incidental in 10 cases (52.6%), in 5 cases (26.3%) there was documented hematuria and flank pain in 2 cases (10.5%). The lesion was identified by CT in 13 cases (68.4%) and by urography in 6 cases (31.6%). In 15 cases (79.0%) a nephrectomy or nephroureterectomy was performed, and in 3 cases (15.78%) a local excision of the lesion by ureterorenoscopy or pielotomy. In 3 cases (15.8%) local relapse has been described, and in one case (5.3%) worsening of the disease in a urothelial cancer (4). Discussion: An analysis of the literature on this rare disease has shown that, despite IP is classified as a benign lesion, in 10% of cases it may be associated with other carcinoma of the urinary tract and in one case out of five may recur or develop into malignancy. Instrumental investigation can not suggest any distinctive features of these lesions such as to allow a differential diagnosis with urothelial carcinoma. In fact in the most of the cases the patients were subjected to nephrectomy or nephroureterectomy. Considering the possible association with malignancy, the tendency of these lesions to relapse and the rare malignant progression, a close follow-up is recommended like the model used for the conventional renal tumor. Conclusion: The IP of the kidney is an uncommon disease, which requires accurate characterization by the pathologist for the risk of malignant lesions and close monitoring by the urologist for the risk of local recurrence or malignant degeneration.