DOI:10.2214/AJR.05.0507
AJR 2006; 187:W415-W417
© American Roentgen Ray Society
MRI of Primary Prostatic Wilms' Tumor in a Young Adult
Tetsuo Maeda1,
Ukihide Tateishi1,
Tadashi Hasegawa2,
Hiroyuki Fujimoto3,
Yasuaki Arai1 and
Kazuro Sugimura4
1 Division of Diagnostic Radiology, National Cancer Center Hospital, 1-1-1,
Tsukiji, Chuo-Ku, Tokyo, Japan 104-0045.
2 Department of Clinical Pathology, Sapporo Medical University, School of
Medicine, Sapporo, Japan.
3 Department of Urology, National Cancer Center Hospital, Tokyo, Japan.
4 Department of Radiology, Kobe University Graduate School of Medicine, Kobe,
Japan.
Received March 23, 2005;
accepted after revision April 22, 2005.
Address correspondence to U. Tateishi.
WEB This is a Web exclusive article.
Keywords: abdomen • abdominal imaging • prostate
Introduction
The occurrence of an extrarenal Wilms' tumor is extremely rare. The most
frequently affected sites discussed in previous reports are the
retroperitoneal and inguinal regions
[1]. To the best of our
knowledge, primary prostatic Wilms' tumor has been documented in only one case
[2]. In that report, however,
imaging findings are not available. Here we present the MRI findings of
primary prostatic Wilms' tumor in a young adult.
Case Report
An 18-year-old man with acute urinary retention was referred to our
hospital on suspicion of a prostatic tumor. Findings at physical examination
were normal except for an extremely enlarged prostate gland on the digital
rectal examination. Routine laboratory test results, including cytologic study
of urine, were all normal. Prostate-specific antigen (PSA) and
-fetoprotein were slightly elevated (5.44 and 53.5 ng/mL,
respectively).
A contrast-enhanced CT showed an approximately 10-cm complex cystic mass in
the pelvis that appeared to be arising from the prostate
(Fig. 1A), displacing the
bladder anteriorly and the sigmoid colon laterally. No evidence of renal
neoplasm or metastatic disease was seen. The mass was of low intensity with
high intensity suggestive of hemorrhage on T1-weighted MR images
(Fig. 1B), and of heterogeneous
high intensity on T2-weighted MR images
(Fig. 1C). On
gadolinium-enhanced MR images, the mass had multiple septations with enhanced
soft-tissue components (Fig.
1D).
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Fig. 1B —18-year-old man with primary prostatic Wilms' tumor. Axial
T1-weighted image (TR/TE, 585/10) shows heterogeneous cystic mass of low
intensity with high intensity (arrow) suggestive of hemorrhage.
|
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An endorectal needle biopsy of the prostate resulted in a diagnosis of
nephroblastoma (Fig. 1E).
Preoperative chemotherapy (vincristine, actinomycin D, ifosfamide, and then
etoposide and cisplatin) was begun, leading to no regression of the prostatic
tumor. Thus, the patient underwent a total cystoprostatectomy with ileal
conduit formation and covering colostomy formation.
The surgical specimen showed a multilocular cystic mass of 8.0 x 6.5
x 6.0 cm with necrotic tissue (Fig.
1F). Histologic examination revealed the presence of tubular and
glomeruloid structures admixed with stromal cells. In addition, granulation
and fibrous changes were also seen, suggestive of influence by the
preoperative chemotherapies. Tumor cells showed immunoreactivity for Wilms'
tumor-1, cytokeratin (AE1/AE3), and vimentin. The diagnosis of primary
prostatic Wilms' tumor was confirmed.
The patient's early postoperative period was uneventful. He was given
postoperative chemotherapy of vincristine, actinomycin D, and doxorubicin HCl
(Adriamycin, Pharmacia). He is still well at his 3-year follow-up without
local or systemic recurrences after the surgery.
Discussion
Wilms' tumor (also referred to as nephroblastoma) occurs most commonly in
the kidneys of pediatric patients. Extrarenal Wilms' tumors are rare. Until
now, fewer than 60 cases have been reported in the English-language
literature. Most of these cases have occurred in the retroperitoneum and
inguinal canal. In addition to those regions, the tumors affect the uterus,
cervix, testis, skin, and even the thorax
[1,
3]. Renal Wilms' tumor
generally occurs before the age of 10 years. Likewise, most extrarenal cases
also occur in young patients, such as in our case.
To our knowledge, this case represents the second case of extrarenal Wilms'
tumor confined to the prostate. Although Casiraghi et al.
[2] reported the first case of
primary prostatic Wilms' tumor, imaging findings are not described in that
report. Thus, the present case is considered to be the first case describing
the radiologic features of this rare tumor.
The radiologic features of Wilms' tumor, whether originating from the
kidney or other sites, are nonspecific in the previous reports. Adult Wilms'
tumor typically presents as a large complex solid mass that may have cystic
components resulting from focal necrosis and degeneration
[4,
5]. The heterogeneous
appearance reported in the earlier case was similar to that of the present
tumor.
The differential diagnosis of primary prostatic Wilms' tumor includes
multiple entities (i.e., metastatic Wilms' tumor, embryonal rhabdomyosarcoma,
carcinosarcoma, giant multilocular cystadenoma, prostatic abscess, cavitary
prostatitis, retention cyst, and cystic degeneration in benign prostatic
hyperplasia), the mass of which can produce cysts in the prostate
[6-9].
In the present case, metastatic Wilms' tumor could be excluded by confirming
the absence of a renal mass. However, it is difficult to diagnose
preoperatively with only imaging techniques such as CT and MRI. A percutaneous
needle biopsy might be a reasonable option
[3,
10].
The origin of extrarenal Wilms' tumors is by no means certain. The presence
of ectopic metanephric blastema cells or the Wilms' tumor gene that causes
transformation of extrarenal primitive mesonephric or pronephric remnants into
Wilms' tumor are both considered in the embryogenesis
[3].
In summary, primary prostatic Wilms' tumor may show a complex cystic mass
on CT and MR images that cannot adequately distinguish Wilms' tumor from other
prostatic tumors. However, early and correct diagnosis is required, because
adult Wilms' tumor has a poor prognosis. Although rare, Wilms' tumor may occur
in an extrarenal location and should be included in the differential diagnosis
of an abdominal mass in young adults.
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Introduction
Case Report
