www.elsevier.com/locate/jpedsurg

Bilateral intrarenal pelvis Wilms’ tumorwith fibroepithelial polyp

Jie Sun*, Wei-jing Ye, Hai-teng Zhao, Cheng-ren Shi

Department of Surgery, Shanghai Children’s Medical Center, Shanghai 200127, China

0022-3468/$ – see front matter D 2005

doi:10.1016/j.jpedsurg.2005.06.018

T Corresponding author.

E-mail address: sunjiefan@hotmail.c

Index words:Intrarenal pelvis Wilms’

tumor;

Fibroepithelial polyp

Abstract Intrarenal pelvis Wilms’ tumor is rare in children. A case of a 28-month-old boy with bilateral

intrarenal pelvis Wilms’ tumor associated with a fibroepithelial polyp is reported in this article. The

tumor was evaluated by ultrasonography, computed tomography, and intravenous pyelography. The boy

underwent bilateral renal pelviotomies. Now he is being treated and followed up by pediatric

oncologists.

D 2005 Elsevier Inc. All rights reserved.

Wilms’ tumor is the second most common malignant

solid tumor in children [1]. It is considered to originate from

the remnants of the embryonic metanephric blastema [2];

hence, it can occur in any part of the kidney but still rarely

seen in the pelvicaliceal system. Herein, we report a case of

bilateral intrarenal pelvis Wilms’ tumor associated with a

fibroepithelial polyp.

1. Case report

A 28-month-old boy was admitted for a 5-month history

of gross hematuria without fever or abdominal pain. He had

an ultrasonographic and a computed tomographic scan in a

local hospital and bilateral pelvicaliceal mass had been

detected. The boy had been treated as Wilms’ tumor with

4 courses of chemotherapy (vincristine 0.05 mg/kg per

week � 4). Hematuria persisted and he was transferred to

our hospital for further diagnosis and treatment. Upon

admission, the boy was generally well with a body weight

Elsevier Inc. All rights reserved.

om (J. Sun).

of 15 kg and no palpable mass was found in the abdomen.

Urinalysis revealed slight microscopic hematuria (white

blood cell, 6-8 per high-power field; red blood cell, 8-10 per

high-power field). A complete blood count of white

blood cell 3.0 � 109/L (4.0-15.0 � 109/L), red blood cell

3.9 � 1012/L (4.0-5.5 � 1012/L), and hemoglobin 97 g/L

(120-160 g/L) was obtained. Additional biochemical

indicators showed lactate dehydrogenase 1709 U/L

(313-618 U/L), blood alpha-fetoprotein 1.47 ng/mL (0-25

ng/mL), and urine vanillylmandelic acid 40.77 lmol per 24

hours (15.66-88.58 lmol per 24 hours). Repeated ultraso-

nography determined the size of the left and right kidney to

be 94 � 40 and 81 � 39 mm, respectively. Computed

tomography (Figs. 1 and 2) of the abdomen showed solid

tumor in both renal pelves. The left-sided tumor was 37� 52

mm and the right-sided one was 35 � 37 mm. Calculi were

visible in the tumor. With contrast, the tumors were enhanced

equally. An intravenous pyelography showed the cortices

were thin by compression and the pelves were slightly

dilated. A dynamic renal scan confirmed normal renal

function bilaterally. No obvious abnormality could be found

in the ureters or the bladder. On the third day of

hospitalization, an operation was performed. In the process

of left renal pelviotomy, it was noted that the calyces were

Journal of Pediatric Surgery (2005) 40, 1670–1672

Fig. 1 Computed tomography demonstrates solid masses with

calculi in bilateral intrarenal pelvis.

Fig. 3 Microscopic appearance of the right pelvic Wilms’ tumor

associated with a fibroepithelial polyp. The tumor cells were in the

lower right part of the picture (original magnification �40).

Bilateral intrarenal pelvis Wilms’ tumor with fibroepithelial polyp 1671

occupied with a smooth botryoid mass, which extended to

the upper part of the ureters. In the superior posterior calyx, a

vascular pedicle was attached to the mass. The mass was

completely removed from the renal pelvis and the cortex was

left undamaged. After resection, the pathological diagnosis

was bleft renal pelvis fibroepithelial polyp associated with a

few primitive tubular and glomeruloid structures in the

interstitium; some nephroblastomoid tissues were found.QBecause of the prolonged operating time, the contralateral

side was not explored at this procedure. After 2-month

follow-up with no medical treatment, the boy was readmitted

to this hospital and underwent a right renal pelviotomy. The

size of the mass from the previous operation remained

unchanged and it was completely resected successfully. The

appearance of the mass was similar to the one in the previous

operation but some part of the cut surface looked homog-

enous and whitish. The pathological report was brightintrarenal pelvis Wilms’ tumor of favorable histology

Fig. 2 Renal parenchyma is attenuated homogenously on both

sides.

Fig. 4 Microscopic appearance of Wilms’ tumor cells in the

�

associated with pelvic fibroepithelial polyp (Figs. 3 and 4);

the tumor was diffusely necrotic and focally calcified.QDuring the entire process of the treatment, the boy was

asymptomatic. After the operation, the boy was transferred to

the oncologists and was determined as Wilms’ tumor of stage

V. Chemotherapy of ifosfamide (1.5 g/m2), vincristine (0.05

mg/kg), and etoposide (303 mg/kg) was given to the patient

according to our protocol [3].

2. Discussion

The conventional Wilms’ tumor usually originates from

the parenchyma of the kidney. It rarely presents as an

intrarenal pelvis extension or a botryoid growth. To our

knowledge, only 23 cases of intrarenal pelvis Wilms’ tumor

were reported to date (excluding the present one) [4]. The

earliest case was reported by Poole and Viamonte [5] in

1970. The patient had a Wilms’ tumor located in the pelvis,

which originated in the lower pole of the left kidney. The

lesion had ruptured early through an inferior calyx to

right renal pelvis (original magnification 100).

J. Sun et al.1672

develop primarily as an intrapelvic mass [5]. Wilms’ tumor

occurring entirely in the pelvicaliceal system with no or

minimal parenchymal involvement is extremely rare, with

only 8 cases reported in the literature [6]. None of them

presented bilaterally. The average age of the patients was

3.3 years. And there were 5 boys and 3 girls. The laterality

of the tumor was similar to the traditional group [6].

Moreover, 87.5% of intrapelvic Wilms’ tumor presented

with hematuria and only 37.5% had a palpable mass on

physical examination [6]. By means of imaging techniques,

the botryoid growth of the mass can be assessed and

generally conforms to the outline of the calyxes. The cortex

is thinned by compression. Complete blood count and

biochemical tests are of little value in diagnostic evaluation.

The pelvis dilates from the obstruction to urinary flow.

Johnson et al [7] suggested that the neoplasm arises in the

renal pelvis, perhaps in the ureteral bud itself, subsequently

extends into the renal sinus, and secondarily involves a

small area of parenchyma.

The 28-month-old patient diagnosed with bilateral

Wilms’ tumor in this report had a lesion associated with a

fibroepithelial polyp. Such a fibroepithelial polyp is also an

uncommon benign mesenchymal tumor of the renal pelvis

and ureter. Most (70%) of the patients are male. Colicky

flank pain and hematuria are the most common symptoms.

In general, these tumors consist of single or multiple

smooth-surfaced slender fronds arising close together from

the mucosa. The most common locations are the ureter-

opelvic junction and upper ureter. Histopathologically, the

polyps consist of a vascular, loose, edematous stromal core

with a variable inflammatory infiltrate, covered by essen-

tially normal urethelium that may show foci of squamous

metaplasia or ulceration [8]. We hypothesize that occur-

rence of the fibroepithelial polyp was stimulated by the

growth of tumor.

The absence of Wilms’ tumor in the left renal pelvis

pathologically was probably attributed to the prior chemo-

therapy delivered at the local hospital. The pathologists could

not detect viable tumor cells or necrotic tissues in the sample.

Although there were some nephroblastomoid tissues found in

this case, the presence of Wilms’ tumor could not be

confirmed. Remnants of the fetal blastema, found in

approximately 1% of infant autopsies, have been recognized

as potential precursor lesions of Wilms’ tumor [4].

It was unfortunate that the patient was not initially

diagnosed and treated according to theWilms’ tumor protocol

before admission to our hospital. Whether it was appropriate

to give chemotherapy before a pathological diagnosis is

determined needs further discussion. As we know, some

European groups (Societe Internationale d’ Oncologie

Pediatrique [SIOP], etc) often treat patients on imaging

studies alone, but we are worried about the misdiagnoses.

Weinberg et al [9] proposed that the intrapelvic Wilms’

tumor should be treated as classical tumors of similar stage

because they demonstrate similar prognosis. This patient

has made a steady recovery. Up till now, there has been

more than 1 year since the initial treatment was performed.

The boy looks asymptomatic with no mass or hydro-

nephrosis that could be detected by ultrasound. Because

the case is so rare, close long-term follow-up is planned.

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