Case 2 -
Cystadenoma of the Prostate
Wellington School of
Medicine and Health Sciences
Wellington, New Zealand
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A 48-year-old male was referred to a specialist surgical centre with a provisional diagnosis of
pseudomyxoma peritonei. In the last 5-6 years, he had noted a steady increase in abdominal girth and
this had become particularly pronounced over the preceding 6 months. During this time he had also noted
a loss of abdominal muscle bulk. He reported no difficulty with micturation or bowel function.
Examination on admission confirmed marked abdominal distension. Computerized tomography showed a
large multicystic mass almost entirely confined to the infracolic compartment, however, somewhat atypical
for pseudomyxoma peritonei was the lack of extensive involvement in the subdiaphragmatic space and
spleen. The patient went forward to laparotomy and a large cystic mass involving the rectosigmoid and
prostate was found. The tumor was removed in two stages with resection of an extensive mass measuring 37
x 31 x 13 cm. Residual tumor was noted to be adherent to the rectum and bladder, and there was an
attachment to the left posterior-lateral surface of the prostate. In the second stage procedure, the
bladder and prostate were removed en bloc with all residual tumor.
Case 2 - Figure 4 - Cystadenoma of prostate, squamous metaplasia of epithelium.
Case 2 - Figure 5 - Cystadenoma of prostate, epithelium shows focal PSA immunoexpression.
Case 2 - Figure 6 - Cystadenoma of prostate, focal areas showing typical prostate architecture.
Sections taken from the tumor showed numerous multilocular cysts lined by simple cuboidal to columnar
epithelium with a prominent underlying basal cell layer. Focally the epithelium formed papillary tufts
while elsewhere there was early squamous metaplasia. In the areas of squamous metaplasia the basal cell
layer was not discernible. Many of the cysts contained basophilic mucin, often intermixed with fibrin,
while in others desquamated epithelial cells were seen. The supporting stroma consisted of fibrous
connective tissue with prominent collagen bundles and strands of smooth muscle. Numerous telangiectatic
vessels and occasional neural bundles were also present. The stroma showed mild to moderate edema and
there was a diffuse inflammatory cell infiltrate consisting of lymphocytes and plasma cells.
In occasional areas within the tumor mass the epithelium and stroma resembled normal prostate tissue
and here the acini contained corpora amylacea.
The tumor was adherent to the serosa of the large bowel and bladder, and blended with the tissue of
the prostate removed during the second stage operative procedure.
Immunohistochemical studies showed prostate specific antigen (PSA) and prostate specific acid
phosphatase (PAP) to be strongly positive in the glandular epithelium, in areas that resembled normal
prostate tissue. Cystically dilated glands showed sparse focal positivity for both PSA and PAP. All
epithelial cells were negative for Cytokeratin 7 and 20. There was almost 100% positivity for estrogen
receptor (ER) alpha in the stroma with positive labeling confined to stromal nuclei. Focal areas of ER
alpha positivity were seen in acinar epithelium exhibiting squamous metaplasia. Progesterone receptor
antigen expression had a similar distribution although both glandular and squamous epithelial elements
showed focal positivity.
Cystadenoma of the Prostate
Cystadenoma of the prostate is a rarely recognized neoplasm and, to date, 12 cases have been reported
in the literature (Table). In the majority of cases either acute or chronic urinary retention was the
presenting symptom, while less frequent symptoms included abdominal mass, hematuria and
abdominal/testicular pain. Patient age ranged from 23 to 80 years (mean 54 years) with 75% of cases
occurring in patients greater than 50 years of age.
Cystadenomas ranged in size from approximately 2 cm to 45 cm in maximum diameter. In the majority of
cases the tumors were situated within the rectovesical space and, while infiltration of adjacent
structures was not seen, tumors were frequently adherent to the serosal surface of the
In the majority of reported cases a connection between the tumor mass and the prostate gland was
determined at operation, and for large tumors - as in the present case - this usually consisted of an
attenuated pedicle. In some cases no pedicle was detected and it was suggested that the prostatic
connection was lost as tumors grew in size and expanded along existing tissue planes. In such cases it
was speculated that the tumor developed a local extra-prostatic vascular supply in a manner somewhat
similar to a parasitic uterine leiomyoma.
An alternative suggestion for the origin of extraprostatic tumors is that they arise in ectopic
prostatic tissue separate from the prostate gland. Prostatic tissue has been reported from a variety of
ectopic sites being most commonly found in the urethra and bladder wall.  Other sites of
ectopic prostatic tissue include the subvesical, retrovesical and pararectal spaces, the anal wall,
pericolic fat, epididymis, penis and testis.
The distribution of ectopic prostatic
tissue indicates that the deposits result either from migration failure of preprostatic
tissue  or from a persistent ability of the tissues of the posterior cloacal compartment -
which form the rectum - to undergo differentiation into prostatic epithelium and stroma. 
Occasional examples of ectopic prostate exhibit extensive cyst formation with apparent stroma
As these are features that associated with cystadenoma, this suggests that
these lesions may represent examples of these tumors in an early stage of evolution.
Published Cases of Cystadenoma of the Prostate
|Author || Age ||Presenting symptoms || Maximum|
|Melen 1932  || 65 yr ||Obstructive symptoms 1 year ||+- 2cm ||Yes|
|Cummine 1950  || 59 yr ||Acute urinary retention ||20cm|| No|
|Blum 1960  || 56 yr ||Obstructive symptoms ||>40 gms|| Yes|
|Pyrah 1964  || 63 yr ||Obstructive symptoms ||7.5cm ||Yes|
|Kendall 1986  || 23 yr ||Testicular pain 18 mths|
Flank pain 18 mths
Nausea and vomiting 18 mths
| 14cm|| No|
|Watanabe 1990 || 80 yr ||Urinary retention|| 11cm ||Yes|
|Maluf 1991  || 28 yr ||Acute urinary retention || 19cm|| No|
|Maluf 1991  || 37 yr ||Obstructive symptoms|
| 45cm|| No|
|Levy 1993  || 56 yr ||Obstructive symptoms 4 mths|
Abdominal distension 3 days
| 13cm|| Yes|
|Lim 1993  || 64 yr ||Obstructive symptoms 3 mths|
Abdominal pain 1 mth
| 17cm|| Yes|
|Kirsch 1996  || 65 yr ||Obstructive symptoms 4 weeks|
Hematuria 3 weeks
| 15cm ||Yes|
|Allen 2003  || 52 yr ||Obstructive symptoms|
The clinical differential diagnosis of cystadenoma of the prostate is somewhat dictated by the site of
the tumor and includes a wide variety of cystic structures of the prostate and periprostatic organs
including simple/multilocular prostatic cysts, seminal vesicle cyst, Müllerian duct cyst, utricular cyst,
ejaculatory duct cyst and inflammatory cyst (abscess) of the prostate. Neoplastic lesions that should be
considered include prostatic sarcoma/phyllodes tumor, retroperitoneal teratoma/sarcoma and cystic
The histological features of cystadenoma permit differentiation of the lesion from cysts of the
periprostatic organs and most tumors, however, the architecture of phyllodes tumor can mimic
cystadenoma. In previous studies phyllodes tumor has been mistaken for cystadenoma,  while a
case of so-called cystadeno-leiomyofibroma, which was included by the authors in the general category of
prostate cystadenoma, shows typical features of phyllodes tumor.  In general, phyllodes
tumor may be differentiated from cystadenoma by the presence of stromal hypercellularity which may or may
not show nuclear atypia. In equivocal cases, ER expression by stroma cells may be helpful as this is not
seen in phyllodes tumor. 
The pathogenesis of these tumors is uncertain and in one case it has been noted that they resemble
benign prostate tissue.  In the present case, the bulk of the tumor shows extensive cyst
formation and bears little resemblance to normal prostate, although focally more typical prostate glands,
often with corpora amylacea, were seen. In much of the tumor, despite the often extensive cyst
formation, there is a relative paucity of epithelial elements and the stroma appears to be the
predominant growth fraction. Evidence of apparent stromal overgrowth may also be deduced from those
areas of the tumor that architecturally resemble fibroadenoma of the breast. The expression of ER alpha
within the stroma of the tumor is of interest and may provide some clues as to the pathogenesis of the
lesion. Normal prostatic tissue shows positive immunostaining for ER alpha in 15% of cells of the
stromal compartment, while only 0.4% of epithelial cells are positive.  More recent studies
have indicated that stroma ER alpha expression is zone dependent, being absent in transitional zone but
present in "occasional" cells within the stroma of the peripheral zone.  In cystadenoma
virtually all stroma cells show positive ER alpha immunoexpression, while expression in epithelial cells
is seen only infrequently. It is possible that cystadenomas arise as a result of tissue hypersensitivity
to estrogens and, as such, the pathogenesis of these lesions would appear to be similar to that proposed
for giant fibroadenoma/virginal hypertrophy of the breast. 
There is some debate in the literature as to appropriate treatment for cystadenoma of the prostate,
with both conservative  and radical surgery  being advocated. In all but one of
the cases treated surgically, either by enucleation or en bloc resection,
there has been no evidence of recurrence. The solitary example of recurrent cystadenoma occurred in a
38-year-old male treated initially by a two-stage procedure with resection of the abdominal component
followed 4 months later by resection of the pelvic component.  Sixteen months after the
initial procedure, tumor recurred in the pelvis and this was treated by pelvic exenteration and
irradiation. Following this, the patient remained tumor-free. The histologic features of the tumor were
similar to other cases of cystadenoma, and in particular there was no evidence of stromal
hypercellularity indicative of phyllodes tumor.
Radical surgery was chosen as the appropriate option in the present case due to the large size of the
lesion and the extensive involvement of the rectum and bladder. At operation no clear dissection plane
was apparent and it was considered that if a conservative approach was followed there would be a high
risk of incomplete resection and possible recurrence.
- Melen DR. Multilocular cyst of the prostate. J Urol 1932; 27:343-349.
- Cummine HG, Johnson AS. Report of a case of retrovesical polycystic tumor of probable prostatic origin. Aust NZ J Surg 1950; 19:91-92.
- Blum E, Batzenschlager A, Le Gal Y. Adenome prostatique cystico-papillaire a évolution polykystique. J d'Urol (Paris) 1960; 66:411-415.
- Pyrah LN. Retrovesical tumors. A report of three cases. Brit J Urol 1964; 26: 75-83.
- Kendall AR, Stein BS, Shea FJ, Petersen RO, Senay B. Cystic pelvic mass. J Urol 1986; 135:550-553.
- Watanabe J. A case of giant prostatic cystadenoma. Acta Urol Jpn 1990; 36: 1077-1079.
- Maluf HM, King ME, DeLuca FR et al. Giant multilocular prostatic cystadenoma. A distinctive lesion of the retroperitoneum in men. A report of two cases. Am J Surg Pathol 1991; 15:131-135.
- Levy DA, Gogate PA, Hampel N. Giant multilocular prostatic cystadenoma. A rare clinical entity and review of the literature. J Urol 1993; 150:1920-1922.
- Lim DJ, Hayden RT, Murad T etal. Multilocular prostatic cystadenoma presenting as a large complex pelvic cystic mass. J Urol 1993; 149:856-859.
- Kirsch AJ, Newhouse J, Hibshoosh H et al. Giant multilocular cystadenoma of the prostate. Urology 1996; 48:303-305.
- Allen EA, Brinker DA, Coppola D, Diaz JI, Epstein JI. Multilocular prostatic cystadenoma with high-grade prostatic intraepithelial neoplasia. Urology 2003; 61:644.
- Kanomata N, Eble JN, Ohbayashi C et al. Ectopic prostate in the retrovesical space. J Urol Pathol 1997; 7:121-126.
- Yasukawa S, Aoshi H, Takamatsu M. Ectopic prostatic adenoma in retrovesical space. J Urol 1987; 137:998-999.
- Gledhill A. Ectopic prostatic tissue. J Urol 1985; 133:110-111.
- Goodale RH. Cystadenoma of the bladder from aberrant prostatic gland. Arch Pathol 1928; 6:210-214.
- Kirkland KL, Bale PM. A cystic adenoma of the prostate. J Urol 1967;97:324-327.
- Cox R, Dawson IMP. A curious prostatic tumor. Probably a true mixed tumor (cystadeno-leiomyofibroma). Brit J Urol 1960; 32:306-311.
- Bostwick DG. Case 5 (Stromal sarcoma arising in phyllodes tumor of prostate) USCAP Genitourinary Specialty Conference Publication 2002, pp 25-34.
- Royuela M, de Miguel MP, Bethencourt FR et al. Estrogen receptors a and b in the normal, hyperplastic and carcinomatous human prostate. J Endocrinol 2001; 168:447-454.
- Tsurusaki T, Aoki D, Kanetake H et al. Zone-dependent expression of estrogen receptors a and b in human benign prostatic hyperplasia. J Clin Endocrinol Metab 2003; 88:1333-1340.
- Baker SB, Burkey BA, Thornton P, La Rossa D. Juvenile gigantomastia: Presentation of four cases and review of the literature. Ann Plast Surg 2001; 46: 517-526.