1. ¹Department of Pathology and Laboratory Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
2. ²Department of Pathology, Chang Gung Memorial Hospital-Kaohsiung Medical Center and Chang Gung University College of Medicine, Kaohsiung, Taiwan
3. ³Department of Pathology, Singapore General Hospital, Singapore
4. ⁴Department of Pathology, Cordoba University, Cordoba, Spain
5. ⁵Department of Urology, Indiana University School of Medicine, Indianapolis, IN, USA

Correspondence: Dr L Cheng, MD, Department of Pathology and Laboratory Medicine, Indiana University School of Medicine, 350 West 11th Street, Clarian Pathology Laboratory Room 4010, Indianapolis, IN 46202, USA. E-mail: Icheng@iupui.edu

Received 3 May 2006; Revised 23 June 2006; Accepted 23 June 2006; Published online 21 July 2006.

Abstract

Inverted papilloma of urinary bladder is an uncommon urothelial neoplasm. Its relationship to urothelial carcinoma is controversial. Little is known of the genetic abnormalities of inverted papilloma. To better understand its genetics, we analyzed 39 inverted papillomas, including 36 from men and three from women, for loss of heterozygosity (LOH). We examined four polymorphic microsatellite markers located on chromosome 9q32–33(D9S177), chromosome 9p22 (IFNA), chromosome 3p14.2 (D3S1300) and chromosome 17p13.1 (TP53), where genetic alterations occur frequently in urothelial carcinomas. Additionally, the status of inactivation of X-chromosome was examined in three female patients. The frequency of LOH in informative cases was 8% (3 of 37) for D9S177, 10% (4 of 38) for TP53, 8% (3 of 37) for IFNA and 8% (3 of 36) for D3S1300. In the analysis of X-chromosome inactivation, all three cases yielded informative results and one had nonrandom inactivation of X-chromosomes. The monoclonal origin demonstrated in the study of X-chromosome inactivation indicates the clonal process of inverted papilloma; however, the low incidence of LOH supports the view that inverted papilloma in urinary bladder is a benign neoplasm with molecular genetic abnormalities different from those of urothelial carcinoma.