rete testis neoplasms and pseudotumors, mesothelial lesions
Selected other problematic testicular and
paratesticular lesions: rete testis neoplasms
and pseudotumors, mesothelial lesions and
secondary tumors
Mahul B Amin
Departments of Pathology, Urology, Hematology and Oncology, Emory University School of Medicine,
Atlanta, GA, USA
The proximity and, in some instances, communication between several structures in the testis and paratestis
(rete testis, epididymis, mesothelium, vestigial epithelium and paratesticular soft tissue) result in a plethora of
interesting tumors and tumor-like lesions that together pose a formidable diagnostic challenge both because of
their morphologic overlap and rarity. The occasional spread of tumors primarily at other sites to this region
adds to the potential problem encountered. This review provides an overview of the pathology of
nonmesenchymal paratesticular neoplasms and pseudotumors with a focus on the approach to tubulopapillary
neoplasms for which diagnostic considerations may include carcinoma of the rete testis, malignant
mesothelioma, ovarian-type epithelial tumors, epididymal carcinoma and metastatic carcinomas. The
cornerstone of accurate characterization of these lesions is still a comprehensive, traditional clinicopathologic
approach, clinical history (of another primary), gross examination (location) and routine light microscopy, but
judicious incorporation of contemporary immunohistochemical markers may aid or in some instances be
crucial in resolving the problems encountered.
Modern Pathology (2005) 18, S131–S145. doi:10.1038/modpathol.3800314
Keywords: paratestis; rete testis hyperplasia; rete testis carcinoma; adenomatoid tumor; malignant mesothelioma; serous neoplasms; mucinous tumors; metastatic carcinoma; immunohistochemistry
Although the great majority of testicular neoplasms
are germ cell tumors and most of the remainder fall
in the sex cord-stromal category, miscellaneous
other neoplasms and pseudotumors of various types
are encountered. They are often both morphologically intriguing and diagnostically challenging.
Although some of these are strictly speaking not
‘gonadal’ inasmuch as they are paratesticular, they
still occur within the scrotal sac and from the
clinical viewpoint the differential diagnosis is
often that of a ‘testicular’ mass. Selected lesions
from within this spectrum of processes are reviewed
here.
Lesions of the rete testis (Table 1)
Non-Neoplastic Rete Epithelial Proliferations
Real or apparent adenomatous hyperplasia of the
rete occurs in association with various testicular
abnormalities, most frequently testicular atrophy.1–3
In these cases, the appearance is probably one of
relative prominence rather than a ‘true’ hyperplasia,
but the distinction between hyperplasia and relative
prominence is arbitrary. Bona fide hyperplasia is
usually an incidental finding and is grossly manifest
as a solid or cystic mass in less than half of the cases.
In these cases, the separation between hyperplasia
and adenoma is also debatable but again of no
clinical importance.
Microscopically, adenomatous hyperplasia is
characterized by a complex interconnecting proliferation of tubulopapillary channels that may be
focal or diffuse and with or without cystic dilatation
(Figure 1).3,4 The lumens may be empty, sperm
containing or have eosinophilic secretion (Figure
Received and accepted 30 August 2004 1b). The lining cells are cuboidal to low columnar
Correspondence: Dr MB Amin, MD, Emory University Hospital,
1364 Clifton Rd., N.E., Atlanta, GA 30322, USA.
E-mail: mahul_amin@emory.org
Modern Pathology (2005) 18, S131–S145
& 2005 USCAP, Inc All rights reserved 0893-3952/05 $30.00
www.modernpathology.org
with innocuous cytology (Figure 1c). Continuity
with nonhyperplastic rete provides clues to a rete
origin and the incidental presentation and usual
background of other testicular pathology indicates a
non-neoplastic nature.
Adenomatous rete testis hyperplasia has been
reported in patients with cryptorchidism, various
nongerm cell tumors and in patients with chronic
hepatic insufficiency and bilateral renal dysplasia.5
In patients with germ cell tumors, another form of
hyperplasia occurs which, in contrast to ‘adenomatous hyperplasia,’ is invariably an incidental finding
and is not grossly cystic.6 In these cases, hyperplastic rete epithelium fills variably expanded channels
often with intracytoplasmic eosinophilic (less than
1 mm to greater than 10 mm) hyaline globules (Figure
2). This pattern may be mistaken for yolk sac tumor,
although the arborizing architecture of the rete is
retained and is diagnostic of the process (Figure
2b).6 The globules most likely represent proteins
absorbed by hyperplastic rete epithelium, which is
stimulated by neoplastic invasion.
Benign Tumors of the Rete Testis
The rare benign tumors of the rete testis (grossly
circumscribed neoplasms microscopically lined by
bland cuboidal to columnar cells sometimes exhibiting transition with normal or hyperplastic epithelium) span a spectrum from solid proliferations of
closely packed tubules (adenoma) to those with
a conspicuous cystic component (cystadenoma), a
papillary architecture (papillary cystadenoma) or a
fibromatous stromal component (adenofibroma).1,5
A distinctive variant with solid tubules resembling
Sertoli cell tumor of the testicular parenchyma has
been reported—sertoliform cystadenoma of the rete
testis.
7 These latter tumors, which are arguably the
most intriguing, have ranged from microscopic to
3 cm, and have all occurred in adults. Dilated rete
channels contain a proliferation of solid tubules
lined by tall columnar cells with eosinophilic to
pale cytoplasm and have basal nuclei with distinct
Figure 1 Adenomatous hyperplasia of rete testis. Complex,
interconnecting proliferation of tubular channels with and without cystic dilatation, low power (a and b). The lining cells are
cuboidal to low columnar with innocuous cytology (c).
Table 1 Cystic change, non-neoplastic rete proliferations and
tumors of rete testis
Cysts
Congenital—simple cysts
Acquired (hemodialysis patients)
Cystic transformation
Congenital—cystic dysplasia
Acquired—multifactorial
Non-neoplastic proliferations
Adenomatous hyperplasia of rete testis
Hyperplasia associated with germ cell tumors
Benign tumors
Adenoma including adenofibroma
Cystadenoma including sertoliform cystadenoma
Malignant tumors
Carcinoma of rete testis
Secondary involvement
Miscellaneous testicular and paratesticular lesions
MB Amin
paratesticular lesions: rete testis neoplasms
and pseudotumors, mesothelial lesions and
secondary tumors
Mahul B Amin
Departments of Pathology, Urology, Hematology and Oncology, Emory University School of Medicine,
Atlanta, GA, USA
The proximity and, in some instances, communication between several structures in the testis and paratestis
(rete testis, epididymis, mesothelium, vestigial epithelium and paratesticular soft tissue) result in a plethora of
interesting tumors and tumor-like lesions that together pose a formidable diagnostic challenge both because of
their morphologic overlap and rarity. The occasional spread of tumors primarily at other sites to this region
adds to the potential problem encountered. This review provides an overview of the pathology of
nonmesenchymal paratesticular neoplasms and pseudotumors with a focus on the approach to tubulopapillary
neoplasms for which diagnostic considerations may include carcinoma of the rete testis, malignant
mesothelioma, ovarian-type epithelial tumors, epididymal carcinoma and metastatic carcinomas. The
cornerstone of accurate characterization of these lesions is still a comprehensive, traditional clinicopathologic
approach, clinical history (of another primary), gross examination (location) and routine light microscopy, but
judicious incorporation of contemporary immunohistochemical markers may aid or in some instances be
crucial in resolving the problems encountered.
Modern Pathology (2005) 18, S131–S145. doi:10.1038/modpathol.3800314
Keywords: paratestis; rete testis hyperplasia; rete testis carcinoma; adenomatoid tumor; malignant mesothelioma; serous neoplasms; mucinous tumors; metastatic carcinoma; immunohistochemistry
Although the great majority of testicular neoplasms
are germ cell tumors and most of the remainder fall
in the sex cord-stromal category, miscellaneous
other neoplasms and pseudotumors of various types
are encountered. They are often both morphologically intriguing and diagnostically challenging.
Although some of these are strictly speaking not
‘gonadal’ inasmuch as they are paratesticular, they
still occur within the scrotal sac and from the
clinical viewpoint the differential diagnosis is
often that of a ‘testicular’ mass. Selected lesions
from within this spectrum of processes are reviewed
here.
Lesions of the rete testis (Table 1)
Non-Neoplastic Rete Epithelial Proliferations
Real or apparent adenomatous hyperplasia of the
rete occurs in association with various testicular
abnormalities, most frequently testicular atrophy.1–3
In these cases, the appearance is probably one of
relative prominence rather than a ‘true’ hyperplasia,
but the distinction between hyperplasia and relative
prominence is arbitrary. Bona fide hyperplasia is
usually an incidental finding and is grossly manifest
as a solid or cystic mass in less than half of the cases.
In these cases, the separation between hyperplasia
and adenoma is also debatable but again of no
clinical importance.
Microscopically, adenomatous hyperplasia is
characterized by a complex interconnecting proliferation of tubulopapillary channels that may be
focal or diffuse and with or without cystic dilatation
(Figure 1).3,4 The lumens may be empty, sperm
containing or have eosinophilic secretion (Figure
Received and accepted 30 August 2004 1b). The lining cells are cuboidal to low columnar
Correspondence: Dr MB Amin, MD, Emory University Hospital,
1364 Clifton Rd., N.E., Atlanta, GA 30322, USA.
E-mail: mahul_amin@emory.org
Modern Pathology (2005) 18, S131–S145
& 2005 USCAP, Inc All rights reserved 0893-3952/05 $30.00
www.modernpathology.org
with innocuous cytology (Figure 1c). Continuity
with nonhyperplastic rete provides clues to a rete
origin and the incidental presentation and usual
background of other testicular pathology indicates a
non-neoplastic nature.
Adenomatous rete testis hyperplasia has been
reported in patients with cryptorchidism, various
nongerm cell tumors and in patients with chronic
hepatic insufficiency and bilateral renal dysplasia.5
In patients with germ cell tumors, another form of
hyperplasia occurs which, in contrast to ‘adenomatous hyperplasia,’ is invariably an incidental finding
and is not grossly cystic.6 In these cases, hyperplastic rete epithelium fills variably expanded channels
often with intracytoplasmic eosinophilic (less than
1 mm to greater than 10 mm) hyaline globules (Figure
2). This pattern may be mistaken for yolk sac tumor,
although the arborizing architecture of the rete is
retained and is diagnostic of the process (Figure
2b).6 The globules most likely represent proteins
absorbed by hyperplastic rete epithelium, which is
stimulated by neoplastic invasion.
Benign Tumors of the Rete Testis
The rare benign tumors of the rete testis (grossly
circumscribed neoplasms microscopically lined by
bland cuboidal to columnar cells sometimes exhibiting transition with normal or hyperplastic epithelium) span a spectrum from solid proliferations of
closely packed tubules (adenoma) to those with
a conspicuous cystic component (cystadenoma), a
papillary architecture (papillary cystadenoma) or a
fibromatous stromal component (adenofibroma).1,5
A distinctive variant with solid tubules resembling
Sertoli cell tumor of the testicular parenchyma has
been reported—sertoliform cystadenoma of the rete
testis.
7 These latter tumors, which are arguably the
most intriguing, have ranged from microscopic to
3 cm, and have all occurred in adults. Dilated rete
channels contain a proliferation of solid tubules
lined by tall columnar cells with eosinophilic to
pale cytoplasm and have basal nuclei with distinct
Figure 1 Adenomatous hyperplasia of rete testis. Complex,
interconnecting proliferation of tubular channels with and without cystic dilatation, low power (a and b). The lining cells are
cuboidal to low columnar with innocuous cytology (c).
Table 1 Cystic change, non-neoplastic rete proliferations and
tumors of rete testis
Cysts
Congenital—simple cysts
Acquired (hemodialysis patients)
Cystic transformation
Congenital—cystic dysplasia
Acquired—multifactorial
Non-neoplastic proliferations
Adenomatous hyperplasia of rete testis
Hyperplasia associated with germ cell tumors
Benign tumors
Adenoma including adenofibroma
Cystadenoma including sertoliform cystadenoma
Malignant tumors
Carcinoma of rete testis
Secondary involvement
Miscellaneous testicular and paratesticular lesions
MB Amin
Comments
Post a Comment