A Case Report of an Inverted Papilloma of the Prostatic Urethra and a Synchronous
Low-Grade Papillary Carcinoma of the Bladder
Copyright © 2012 SciRes. OJPathology
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3. Discussion
Inverted papilloma of the urinary tract is a rare benign
tumor most commonly diagnosed in older men present-
ing with hematuria or symptoms of lower urinary tract
obstruction [3,4]. It is most frequently identified in the
bladder neck or trigone as a polypoid growth with a
smooth surface. These lesions are usually small (<3 cm)
but can be large. Most are solitary although 1% - 4%
may be multifocal.
Histologically there are two main subtypes of inverted
papillomas; trabecular and glandular [1]. The former is
characterized by widely branched, anastomosing cords of
urothelial cells originating directly from the overlying
transitional epithelium. The latter is characterized by
multiple round to oval islands of proliferating urothelial
cells together with pseudoglandular and true glandular
structures, which are often connected with the surface
urothelium.
Although inverted papilloma is generally regarded to
be a benign neoplasm, sporadic cases of inverted papil-
loma with malignant features have been reported raising
concern that inverted papilloma may be a precursor le-
sion of utorhelial malignancy [5-8]. However most of
these patients had a history of previous or concurrent
urothelial carcinoma. Inverted papilloma is associated
with a low risk of recurrence (5%), in marked contrast to
the high recurrence rates of papillary urothelial carci-
noma [3]. Sung et al. [2] reported only one recurrence
among 75 patients with inverted papilloma (1.3%) during
a mean follow-up of 68 months after treatment. The au-
thors recommend that complete transurethral resection
appears to be adequate surgical therapy for inverted
papilloma [2].
The present case showed an inverted papilloma of the
prostatic urethra and a synchronous low-grade non-inva-
sive papillary urothelial carcinoma of the bladder. Spo-
radic cases with inverted papilloma have been reported to
show metachronous or synchronou s urothelial carcinoma.
Brown and Cohen in a series of 41 cases of inverted
papilloma reported 2 patients (4.9%) had a history of
urothelial carcinoma and one of the 2 (2.4%) was diag-
nosed with concomitant urothelial carcinoma [4]. The
authors recommend ed postoperativ e surveillance because
2 patients developed urothelial carcinoma among 25 pa-
tients during a 9 - 25 months cystoscopic follow-up for
non-recurrent inverted papilloma.
Differential diagnosis of inverted papilloma from other
inverted urothelial lesions rests primarily on morpho-
logical criteria. Recognition of the possibility o f inverted
papilloma in the differential diagnosis remains the best
safeguard against incorrect diagnosis [9]. The differential
diagnosis includes non-neoplastic lesions such as von
Brunn’s nest, florid von Brunn’s nest proliferation, cysti-
tis cystica and cystitis glandularis as well as neoplastic
lesions such as inverted urothelial carcinoma, nested
variant of urothelial carcinoma and verrucous squamous
cell carcinoma.
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