Round cell liposarcoma of scrotum with indolent course in young adult.

Abstract

Myxoid/Round cell liposarcoma accounts for one-half of all liposarcomas and occurs as the second most common subtype. Both myxoid and round cell types share clinical, histological features and are accepted to represent a spectrum of lesions ranging from pure myxoid to near completely round cell liposarcoma. Round cell liposarcoma is highly metastatic and is classified as high grade and poorly differentiated myxoid sarcoma. Typical non-round cell myxoid liposarcoma is less metastatic and has more favorable prognosis. Karyotypic study of myxoid and round cell liposarcomas reveal a characteristic reciprocal translocation t (12;16)(q13;p11) resulting in the fusion of CHOP gene with TLS gene in more than 90% of cases. Most masses within the scrotal sac arise from the testis proper, and less likely from the extratesticular tissue. Liposarcoma represents approximately 20% of malignant extratesticular neoplasms, with the well differentiated subtype being the most common. Myxoid/round cell liposarcoma and round cell liposarcoma are rarely encounter in extratesticular soft tissue. We reported a rare case of round cell liposarcoma (high grade myxoid liposarcoma) of extratesticular tissue. To our knowledge, this is the first case of a large size (> 5cm) round cell liposarcoma arising from soft tissue within the scrotal sac of young adult with indolent course. Simple excision or enucleation are inadequate therapies and wide excision of the hemiscrotum including inguinal soft tissue and nodes is recommended. The role of retroperitoneal lymph node dissection and adjuvant chemotherapy remains controversial.

Full text

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1302J Med Assoc Thai Vol. 88 No.9 2005
Correspondence to : Thanakit V, Department of Pathology,
Faculty of Medicine, Chulalongkorn University, Bangkok 10330,
Thailand. Phone: 0-2256-4235 ext 316
Round Cell Liposarcoma of Scrotum with Indolent
Course in Young Adult
Voranuch Thanakit, MD*,
Scott D Nelson, MD**, Suthep Udomsawaengsup, MD***
* Department of Pathology, Faculty of Medicine, Chulalongkorn University
** Department of Pathology, UCLA School of Medicine, Los Angeles, CA, USA
*** Department of Surgery, Faculty of Medicine, Chulalongkorn Univeristy
Myxoid/Round cell liposarcoma accounts for one-half of all liposarcomas and occurs as the second
most common subtype. Both myxoid and round cell types share clinical, histological features and are accepted
to represent a spectrum of lesions ranging from pure myxoid to near completely round cell liposarcoma.
Round cell liposarcoma is highly metastatic and is classified as high grade and poorly differentiated myxoid
sarcoma. Typical non-round cell myxoid liposarcoma is less metastatic and has more favorable prognosis.
Karyotypic study of myxoid and round cell liposarcomas reveal a characteristic reciprocal translocation t
(12;16)(q13;p11) resulting in the fusion of CHOP gene with TLS gene in more than 90% of cases. Most masses
within the scrotal sac arise from the testis proper, and less likely from the extratesticular tissue. Liposarcoma
represents approximately 20% of malignant extratesticular neoplasms, with the well differentiated subtype
being the most common. Myxoid/round cell liposarcoma and round cell liposarcoma are rarely encounter in
extratesticular soft tissue. We reported a rare case of round cell liposarcoma (high grade myxoid liposarcoma)
of extratesticular tissue. To our knowledge, this is the first case of a large size (> 5cm) round cell liposarcoma
arising from soft tissue within the scrotal sac of young adult with indolent course. Simple excision or enucle-
ation are inadequate therapies and wide excision of the hemiscrotum including inguinal soft tissue and nodes
is recommended. The role of retroperitoneal lymph node dissection and adjuvant chemotherapy remains
controversial.
Keywords: Round cell liposarcoma, Scrotum, Young adult, Indolent course
J Med Assoc Thai 2005; 88 (9): 1302-7
Full text. e-Journal: http://www.medassocthai.org/journal
Liposarcoma is the second most common
soft tissue tumor in adults, with an incidence ranging
from 9.8 to 16.0%(1,2). Myxoid/Round cell liposarcoma
accounts for one-half of all liposarcomas and occurs
as the second most common subtype(3). This subtype
is classified according to its histologic, biologic, cyto-
genetic, and molecular characteristics. The behavior of
each subtype is variable ranging from local recurrence
to metastasis. According to the 2002 World Health
Organization (WHO) histologic classification of tumors,
liposarcoma can be divided into 5 categories: atypical
lipomatous tumor/ well differentiated; dedifferentiated;
myxoid; pleomorphic; and mixed-type liposarcoma.
Round cell liposarcoma and the mixed myxoid and
round cell types have recently been subclassified
under the heading of myxoid liposarcoma and mixed-
type liposarcoma(4). These distinctions are problem-
atic in routine usage. The Evans classification system
is practical and easier to use. This system divides
myxoid and round cell liposarcoma into three sub-
groups depending on the relative amount of round cell
components. Tumors with a round cell component
totaling < 10%, 10-25%, and > 25% are defined as
myxoid, mixed myxoid and round cell, and round cell
liposarcoma, respectively(5). Both myxoid and round
cell types share clinical, histological, and cytogenetic
features and are accepted to represent a spectrum of
lesions ranging from pure myxoid to near completely
round cell liposarcoma. Karyotypic evaluation of both
Case Report

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J Med Assoc Thai Vol. 88 No.9 20051303
myxoid and round cell liposarcoma characteristically
reveals the reciprocal translocation t (12;16) (q13;p11)
in more than 90% of cases, resulting in the fusion of
the CHOP and TLS genes(6). However, these tumors
exhibit a distinctly different clinical behavior. Round
cell liposarcoma tends to metastasize and is classified
as a poorly differentiated, or high grade sarcoma. Myxoid
liposarcoma without a round cell component is consi-
dered a low to moderate grade sarcoma and has less
metastatic potential and a more favorable prognosis
than the high grade round cell type(7).
Masses within the scrotal sac are most com-
monly located within the testis and less likely in the
extratesticular tissue. Paratesticular tumors are most
commonly benign (70%) and arise from the spermatic
cord. Despite being relatively rare, malignant neo-
plasms, including sarcomas, do occur. Of these, liposa-
rcoma is encountered about 20% of the time and the
most common subtype is a well-differentiated liposar-
coma, predominantly lipoma-like(8).
Liposarcoma is primarily a tumor of older
adults, with a peak incidence of 40-60 years of age.
Most cases arise within the retroperitoneal or intra-
abdominal regions. The peak age group of myxoid
round cell liposarcomas is the fifth decade and the most
preferential site is the lower extremity, especially the
medial thigh and popliteal fossa(9). To the authors know-
ledge, this is the first case of a large size (> 5cm) round
cell liposarcoma (High grade myxoid liposarcoma)
arising from the soft tissue within the scrotal sac of a
young adult with indolent course.
Case Report
A 34-year-old Thai man presented with a left
scrotal mass of approximately 6 months duration. He
complained of only dull pain and no other symptoms.
The tumor had progressively enlarged but was not
tender. The first clinical impression was that of a
hydrocele. Physical examination revealed a well-circum-
scribed, mobile and soft left scrotal mass with smooth
surface. A CT scan of the abdomen was normal. Opera-
tive findings showed a well encapsulated, smooth-
surfaced mobile mass localized within the scrotum. The
mass was not adherent to the testis and was easily
removed. A wide excision was performed. Laboratory
investigation revealed β-HCG = < 5 mU/ml, Alpha-feto-
protein = 2.2 IU/mL. CXR-PA was within normal limit.
CT-SCAN whole abdomen: No ascitis was noted. No
significant enlarged lymph node was detected.
Pathologic examination revealed a well-defined
tumor mass measuring 8.0 x 6.0 x 4.0 cm. It was multi-
nodular with fibrous encapsulation and had an inho-
mogeneous grey-white cut surface. The percentage of
tan and gelatinous area was approximately 10% of the
whole mass (Fig. 1).
Histological examination showed solid
sheets and islands of round to oval shaped cells with
slightly vacuolated cytoplasm. The round cells showed
moderate pleomorphism, high nuclear/cytoplasmic
ratio, conspicuous nucleoli, and small amounts of
eosinophilic cytoplasm. At the initial sampling, no
myxoid areas were seen. Additional tissue sampling
from the tan gelatinous area revealed focal areas of
univacuolated lipoblasts and a few multivacuolated
cells within the background of myxoid stroma and
chicken-wire capillary vascular pattern. All slides were
examined to identify lipoblasts, round cells, solid and
myxoid areas to determine the percentage of round cell
component. The round cell component represented
approximately 90% of the sampled tumor (Fig. 2A).
Extracellular mucin, including pooling of mucin, admixed
with a small amount of round cells and lipoblasts
was identified and represented about 10% of the tumor
(Fig. 2B). Mitotic figures were present at a rate of 3/10
HPFs. Areas of necrosis and hemorrhage were not
found. Immunohistochemical staining revealed posi-
tivity for S-100 protein (Fig. 3A) and negativity for
lymphocyte common antigen (LCA). Ultrastructural
study revealed lipoblasts with variably sized lipid
droplets as well as primitive cells devoid of lipid
droplets (Fig. 3B).
Discussion
Benign and malignant paratesticular soft
tissue neoplasms represent 52% of all paratesticular
Fig. 1
Multinodular mass with grey-white cut surface
and 10% of tan and gelatinous area of the whole
mass

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1304 J Med Assoc Thai Vol. 88 No.9 2005
Fig. 2A
Solid sheets and islands of round to oval shaped
cells with slightly vacuolated cytoplasm within
background of myxoid stroma and chicken-wire
capillary vascular pattern
Fig. 2B
The round cells shows round to oval shaped
nuclei with high nuclear-cytoplasmic ratio, visible
nucleoli, and less cytoplasm
tumors reported by the Canadian Reference Center of
Cancer Pathology from 1949 to 1987 accounted for
about 52 % of all paratesticular tumors(8). The most
common benign tumors include lipoma, adenomatoid
tumor and leiomyoma. Malignant tumors of the
paratesticular soft tissue are very uncommon. The
percentage of various types of paratesticular sarco-
mas has been previously reported as follows: Leiomyo-
sarcomas (32%), rhabdomyosarcomas (24%), liposar-
comas (20%), and malignant fibrous histiocytomas
(13%)(10).
Liposarcomas in the paratesticular region can
either arise de novo from adipose tissue around testis
and spermatic cord or possibly from a pre-existing
lipoma(11). Previously reports of liposarcoma subtypes
included well-differentiated, myxoid/round cell and
pleomorphic types, with the most frequent subtype
being well-differentiated liposarcoma. These typically
present in older adults as a large mass in paratesticular
region, and tend to recur if incompletely excised.
The preoperative impression of an otherwise
asymptomatic tumor mass in the paratesticular region
can lead to an initial misdiagnosis of a hydrocele, as
was the case in the presented patient. At surgery the
tumor mass was large but was easily separated from
the testis and there was no evidence of infiltration to
surrounding tissue. Grossly, the tumor was rather firm
and solid. As round cell liposarcoma is considered a
poorly differentiated, high grade sarcoma with an
unfavorable prognosis, it is important that all myxoid
liposarcomas be extensively sampled in order to detect
round cell components. Additionally, in the setting of
any small round cell tumor occurring in this region,
round cell liposarcoma must be considered in the
differential diagnosis along with lymphoma, rhab-
domyosarcoma, poorly differentiated (round cell)
synovial sarcoma, and other small round cell tumors.
Kilpatrick et al. showed a relationship between the rate
of metastasis and the percentage of round cell compo-
nent in myxoid/round cell liposarcoma. Round cell

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J Med Assoc Thai Vol. 88 No.9 20051305
recommends wide excision of the hemiscrotum includ-
ing inguinal soft tissue and nodes(13). The roles of
retroperitoneal lymph node dissection and adjuvant
chemotherapy remain controversial.
The majority of reported cases of scrotal
liposarcoma are well differentiated liposarcoma with
low grade behavior. The presented patients prognosis
would appropriately be considered less favorable given
the high grade histology of this tumor. Favorable
prognostic factors in the presented patient include
younger age, absence of spontaneous necrosis,
relative superficial location of the tumor and ease of
complete excision. These may help to explain the
indolent course in the presented patient with a histo-
logically high grade sarcoma. The surgeon plans to do
left a hemiscrotectomy and groin node dissection after
the pathological diagnosis.
It can be seen from this case that upon
encountering a large, painless, cystic or solid mass
in the paratesticular scrotal region, included in the
differential diagnosis should be rare primary mesen-
chymal tumors including sarcomas. With this differen-
tial diagnosis in mind, the appropriate approach to
pathologic examination as well as patient management
is facilitated.
Fig. 3A
The immunohistochemistry study for S-100
protein is positive in nucleus of tumor cells
Fig. 3B
Ultrastructural study reveals lipoblasts with vari-
ably sized of lipid droplets within cytoplasm. The
adjacent primitive cell is devoid of lipid vacuoles
components of 0-5, 5-10, > 25% correlated with the
likelihood of metastasis of 23%, 35%, and 58%, respec-
tively. Overall, patients with myxoid/round cell liposa-
rcomas metastasized at a rate of 35%, with a tumor
related mortality of 31%(11) In tumors with a small round
cell appearance in the 40-60 year old age group, the
most likely entities for consideration in the differential
diagnosis include lymphoma and round cell liposar-
coma. In such a tumor with a great preponderance of
round cells, immunohistochemistry can be useful in
separating these two entities. While lymphoma would
be exhibit positivity for leukocyte common antigen
and negativity for S-100, round cell liposarcoma would
be expected to show the opposite result with LCA nega-
tivity and S-100 positivity. If indicated, ultrastructural
examination can confirm the lipogenic differentiation
of the cells.
Soft tissue sarcomas often locally recur after
incomplete excision. Risk factors for local recurrence in
this region include large size, inguinal location, and
close or positive margin after resection(8). Factors asso-
ciated with significantly poor prognosis are age > 45
years, round cell component > 25%, and the presence
of spontaneous necrosis(12). Catton et al. suggested
that simple excision or enucleation is inadequate and

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