# Müllerian Serous Cystadenoma of the Scrotum Following Orchiopexy

Authors: Sebastian C. J. van der Putte; Johan Toonstra; Daisy M. D. S. Sie-Go
Journal: Advances in Urology
 (2009)

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## Abstract

A 24-year-old man presented himself with a nodular lesion of about 1 cm diameter at the site of a previous orchiopexy associated with surgery for cryptorchism. Histopathology revealed the lesion to be adenomatous and confined to the scrotum. Histological and immunohistological features were not consistent neither with median raphe cysts or cutaneous adenomas nor with the intrascrotal adenomas of the rete testis, epididymis, nor with (malignant) mesotheliomas.  However, the lesion did compare well with serous (papillary) cystadenomas of the testis or paratestis.  These adenomas are thought to originate in remnants of the Müllerian system or of peritoneal lining altered by Müllerian metaplasia. This implies that the scrotal adenoma may have developed from an implant of such elements during orchiopexy 14 years ago. Complete excision of the lesion appears to be an adequate therapy.


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## Body

## 1. Introduction

Tumors and tumor-like lesions in the scrotum comprise
a wide spectrum of conditions related to the scrotum and to the testis and
paratestis [1, 2]. These two categories of “scrotal” and “intrascrotal” lesions
are strictly separated by the anatomical barrier of the tunica vaginalis.In 2004, Hara et al. [3] described an adenomatous
tumor which appeared to have developed at the site of an orchiopexy performed
two weeks earlier and involved the scrotum as well as the testis. They
diagnosed the lesion as a median raphe cyst with features of a borderline
serous cystadenoma. In 2007, Dehner et al. [4] reported a patient with a
similar condition who had been operated on seven years earlier and classified
the lesion as a median raphe cyst. We present a third case which offered an
extra diagnostic challenge by absence of involvement of the testis or paratestis. On the basis
of histopathological criteria, we dismiss the diagnosis of median raphe cyst
and classify the disorder as a serous cystadenoma originating in a Müllerian
implant in the scrotum.


## 2. Case Presentation

A 24-year-old male noticed a circumscribed swelling
in the skin of his left scrotum. Physical examination showed a 1.5 cm nodus at
the site of an orchiopexy performed for cryptorchism 14 years earlier. It was
excised under local anesthesia under the suspected diagnosis of pilar cyst. No
connection with intrascrotal structures was noticed.Macroscopy showed an ellipsoid2.5×1.5×1cm specimen
with a firm 1 cm tumor. Microscopic sections revealed an irregular tubulocystic
epithelial proliferation surrounded by a mantle of connective tissue and
embedded in the smooth musculature of the dartos fascia (Figure 1(a)). The
tumor was completely removed with a very narrow free margin. The tubulocystic
element spread outward from a central sinus that opened externally at the
surface of the skin and was lined by a cornifying stratified squamous
epithelium (Figure 1(a)). Metaplastic noncornifying stratified squamous
epithelium in the deepest part of the sinus passed into columnar to cuboidal
epithelium in the tubulocystic component of the tumor (Figure 1(b)). In
addition to the tubulocystic element, slit-like and papillary configurations
were also observed (Figures
1(c), 1(d)). Variable numbers of cells showed prominent apical snouts or cilia
(Figures 1(d), 1(e)).
The epithelium was bland, mitotic figures were rare, and microinvasion was
absent. Psammona bodies were not observed.Histological
and immunohistochemical features of the scrotal serous cystadenoma at the side
of an orchiopexy 14 years earlier. (a)
Low magnification shows a tubulocystic tumor (between large arrowheads)
surrounded by connective tissue and embedded in the dartos fascia (asterisks).
Note its connection to the epidermis by a sinus (1) lined by cornifying
stratified squamous epithelium and opening at the surface (arrow). (b) Detail of metaplastic noncornifying
stratified squamous epithelium (2) passing into a single-layered columnar
epithelium of the tubulocystic system (3) in the deepest part of the sinus. (c) Cystic papillary component. (d) Detail of a fibrous papilla covered
by characteristic tall columnar epithelium with ciliated cells (small
arrowheads). (e) Cytological and immunohistochemical characteristics discriminating
the tumor from other scrotal and intrascrotal lesions. Vim: Vimentin; ER: Estrogen receptor; PR: Progesterone receptor; Calret: Calretinin; SMA: Smooth muscle actin.
(a)(b)(c)(d)(e)A specially selected differential diagnostic panel of
immunohistochemical tests demonstrated reactivity for cytokeratin (CK) 7 (Biogenex, San Ramon, USA),
vimentin (DAKO, Glastrup, Denmark), Ca-25 (Novocastra, Newcastle, UK),
estrogen receptor (ER),
progesterone receptor (PR) (DAKO), nonreactivity for CK 20 (DAKO), calretinin (Klinipath, Duiven, The Netherlands),  and alpha-smooth muscle actin (SMA)  (Sigma, St Louis, USA). This profile was inconsistent with scrotal median raphe
cysts (nonreactive for vimentin) (three cases tested) and cutaneous papillary
hidradenomas (reactive for SMA in myoepithelium) (three cases tested). With
respect to the possibility of a derivation from paratesticular structures (three cases tested),
the immunoprofile of the tumor did not match those of the rete testis and
mesothelium (nonreactive for Ca-125, ER, and PR, but reactive for calretinin)
or epididymis (nonreactive for Ca-125 and variably reactive for vimentin, ER,
and PR). However, in concordance with cytological details, the profile of the
tumor is similar to that of serous (papillary) cystadenoma of the ovary (three
cases tested). The MIB1 cell proliferation index was 1.5%.


## 3. Discussion

The present case appears to be almost identical in
clinical and histopathological aspects to those described by Hara et al. [3]
and Dehner et al. [4]. It differed in the longer interval between the
orchiopexy and the manifestation of the anomaly and its confinement to the
scrotum. Their argumentation, in favor of a classification of the lesion as a
median raphe cyst though, was not convincing.Median raphe cysts are localized in the midline
between the preanal perineum and the external urinary meatus and typically show
a urethra type of epithelium which is pseudostratified columnar epithelium with
occasional mucus production or cilia and often undergoes squamous metaplasia [5–8] (own
unpublished observations in 19 cases). Cysts near the meatus predominate and
can be explained by a derivation from ectopic urethral glands [9]. Cysts (and
canals) related to the rest of the raphe, which is at some distance from the
urethra and its glands, are thought to have grown from the embryonic urogenital
sinus epithelium which
had remained in the raphe after it had been formed by fusion of the urethral
folds during the formation of the phallic urethra [5, 7, 8]. This theory has to
be dismissed as it has recently been established that such fusion does not take
place [10]. However, the idea that raphe cysts derive from urogenital sinus
epithelium can be upheld as the same study also revealed that this epithelium
temporarily lines the cloacal groove which derives from the middle segment of
the cloaca between the urogenital and anal compartments of the cloaca and at
the surface of the perineum elongates into the male raphe later. Both the
urethra type of epithelium and the direct relationship with the raphe are
lacking in the lesions described by Hara et al. [3] and Dehner et al. [4] and
also in our case.The possibility that the lesion had developed from
cutaneous glands had to be discarded as well. Such adenomas characteristically
show a basal layer of smooth muscle actin-positive myoepithelium [11] which was missing in our case.The absence of a primarily scrotal alternative
diagnosis, the localization at the site of the orchiopexy, and the involvement
of the paratestis
as reported by Hara et al. [3] and Dehner et al. [4] suggest a paratesticular
derivation. Among the adenomatous tumors in this category, the adenomatoid
tumor [1, 12, 13] and papillary cystadenoma of the epididymis [1, 12–14] have a
distinctly different morphology and a different immunoprofile. The cystadenoma
of the rete testis and (malignant) mesothelioma may have a certain
morphological resemblance but differ in immunoprofile especially by showing
reactivity for calretinin [12].The histological and immunohistochemical features of
the lesion were indeed well in accordance with those of the serous (papillary)
cystadenomas of the paratestis (and ovary) [12, 13, 15] as discovered by Hara
et al. [3]. These serous cystadenomas are rare tumors which become manifest as
a painless swelling in mostly middle-aged men and appear to be similar to their
ovarian counterparts. Mild atypia in combination with stratification may lead
to the suspicion of borderline malignancy but prognosis after complete removal
was excellent [13]. Mitotic activity was low.These cystadenomas are thought to originate in
remnants of the Müllerian (paramesonephric) system and/or by Müllerian
metaplasia of the peritoneal lining of the tunica vaginalis [1, 12]. In the
present specific situation of an isolated scrotal localization, this would mean
that the lesion is the result of implantation of Müllerian tissue in the
incision for the orchiopexy. It is not clear if the external opening in our
patient and the drainage in the case of Dehner et al. [4] are a primary or
secondary event.The precise nature of the tumor is still obscure. The
presumed development of the lesion of Hara et al. [3] within two weeks after
the operation appears highly unusual for an adenoma. The report of three cases
of this adenoma in relation with orchiopexy as compared with the report of less
than 40 cases of testicular and paratesticular cystadenoma in the general male population [12] is remarkable and  suggests some sort of special stimulus on the ectopic tissue. The growth of the
tumor over a twenty-one-month period as observed by Hara et al. [3]
demonstrates a progressive character. Their grading of the lesion as a
borderline malignancy may be disputed because mild atypia in some epithelial
cells as the only indicator falls far short of criteria currently applied to
the ovarian counterpart [16]. The disease-free follow-up periods of at least 40
months [3] and 14 months (our patient) suggest that, like the testicular or paratesticular
cystadenoma, complete excision may be adequate but it is evident that more data
are needed.


## 4. Conclusions

Orchiopexy may
be complicated by an adenomatous tumor morphologically identical to the
Müllerian serous (papillary) cystadenoma of the paratestis. Confinement of the
present lesion to the scrotum suggests implantation of Müllerian elements
during the operation. The previous designation “median raphe cyst mimicking a
serous borderline tumor” is incorrect. The still-limited data available suggest
that complete excision may be an adequate therapy.



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