[A clinico-pathological study of inverted papilloma of the urinary bladder. Analysis of histogenesis]

A clinico-pathological study was conducted on 9 cases with inverted papilloma of the urinary bladder. 1. Clinical study: The incidence of inverted papillomas, when compared with transitional cell carcinoma of the urinary bladder, was much higher in men than in women in our study and in the literature dealing with this subject as well. Eight of 9 inverted papillomas were localized in the bladder neck. Cystoscopic examination revealed that all tumors were pedunculated and 8 of the 9 tumors had non-papillary surfaces. These clinical findings suggest that inverted papillomas localized in the bladder neck are very similar to posterior urethral polyps with prostatic type epithelium. Transurethral resection (TUR) was performed in all cases. Recurrence was not observed. 2. Pathological study: Inverted papillomas were classified into two types according to their histological patterns, determined by Hematoxylin-Eosin (H-E) staining. One pattern was glandular and the another was trabecular. Of the 9 cases, 2 were glandular, 5 were trabecular and the remaining 2 were a mixed type. Immunohistochemical staining with anti-prostate specific antigen antibody revealed 3 of the 9 tumors were stained positively, and these tumors were classified a glandular type. Inverted papilloma were classified into two patterns according to their histological patterns, determined by immunohistochemical staining with anti-keratin antibody, namely a bladder tumor pattern and a urethral tumor pattern. Inverted papillomas with a urethral tumor pattern were of the glandular type and included anti-PSA antibody positive staining tumors. These findings suggest that a portion of inverted papillomas may have arisen from neoplastic transformation of prostatic tissue.