212J Nippon Med Sch 2008; 75 (4)
A Surgical Case of Giant Malignant Mesenchymoma in the Posterior
Mediastinum That Recurred in the Bilateral Mediastinum
Shigeo Tanimura1,2, Yuji Saito1,2, Kazuo Honma3and Kiyoshi Koizumi1
1Department of Biological Regulation and Regenerative Surgery, Graduate School of Medicine, Nippon Medical School
2Department of Thoracic Surgery, Nippon Medical School Tama Nagayama Hospital
3Department of Pulmonary Medicine, Sagamihara Kyodo Hospital, Kanagawa
Malignant mesenchymoma is a soft-tissue tumor arising preferentially in the extremities
and the retroperitoneum. We report a case of primary malignant mesenchymoma of the left
side of the posterior mediastinum with local recurrence on both sides of the mediastinum. A
24-year-old woman was admitted to our hospital complaining of cough. Chest X-ray showed a
giant mass in two-thirds of the left lung field, and computed tomography of the chest revealed
a lobulated large mass with a fat-density area and a calcified spot in the mediastinum and left
pleural space. Magnetic resonance of the chest demonstrated a large, solid mass consisting
mainly of areas with the same intensity as fatty tissue and partly of areas of heterogeneous
moderate intensity. The tumor was resected completely through a left posterolateral
thoracotomy. The pathologic diagnosis was malignant mesenchymoma: well-differentiated
liposarcoma with osteocartilagenous differentiation. The patient had local recurrence in both
sides of the mediastinum 3 years and 6 months after surgery, and the recurrent tumors were
completely resected again.
(J Nippon Med Sch 2008; 75: 212―215)
Key words: malignant mesenchymoma, mediastinal tumor, local recurrence
Malignant mesenchymoma is a tumor consisting of
two or more types of well-differentiated sarcoma
posterior mediastinum, which recurred on both sides
of the mediastinum 3 years and 6 months after
resection and was treatable with further surgery.
The patient was a 24-year-old woman who had
severe cough starting in early May 2002 and visited
the Respiratory Department of Sagamihara Kyoudo
Hospital in July. A chest X-ray examination showed
a shadow of a giant mass in the left side of the
thorax (Fig. 1), and the patient was admitted for
emergency treatment. Computed tomography (CT)
and magnetic resonance imaging (MRI) of the chest
suggested a giant mediastinal tumor (specifically, a
teratoid tumor), and the patient was transferred to
Correspondence to Shigeo Tanimura, Department of Thoracic Surgery, Nippon Medical School Tama Nagayama
Hospital, 1―1―7 nagayama, tama-shi, Tokyo 206―8512, Japan
Journal Website (http:? ? www.nms.ac.jp? jnms? )
Malignant Mesenchymoma in the Mediastinum
J Nippon Med Sch 2008; 75 (4) 213
F i g . 1 C h e s t r a d i o g r a p h s h o wi n g a g i a n t ma s s
o c c u p y i n g t wo - t h i r d s o f t h e l e f t s i d e o f t h e
t h o r a c i c c a v i t y .
F i g . 2 C h e s t C T s h o wi n g a g i a n t t u mo r c o n s i s t i n g
o f mi x e d r e g i o n s wi t h i n t e n s i t i e s c o n s i s t e n t
wi t h f a t t y t i s s u e a n d c a l c i f i c a t i o n o c c u p i e d
t wo - t h i r d s o f t h e l e f t s i d e o f t h e t h o r a c i c
c a v i t y a n d c o mp r e s s e d t h e l u n g i n a n
a n t e r i o r a n d u p wa r d d i r e c t i o n .
the Department of Thoracic Surgery at the end of
The physical findings on admission were height,
150 cm; body weight, 50 kg; body temperature,
Respiratory sounds of the left lung were markedly
reduced on auscultation, but no rales were heard.
There were no abnormalities on laboratory tests,
except for a C-reactive protein level of 5.5 mg? dL
and a white blood cell count of 6,800? µL. Respiratory
function tests could not be performed, but the
results of arterial blood gas analysis (under normal
pressure) were normal: PaO2, 92 torr; and PaCO2, 38
torr. Tumor marker findings were normal. On chest
CT, a giant tumor with areas of mixed density
occupied two-thirds of the left side of the thoracic
cavity which compressed the lung in an anterior and
upward direction (Fig. 2). On MRI, the lung was
partly visible in the upper anterior region of the
field, but the tumor occupied most of the view, with
various mixed fatty and calcified components. The
diaphragm was compressed downward. On the basis
of these findings, we concluded on the basis of the
fatty tissue and calcification that the tumor that
originated in the posterior mediastinum was a
At the end of July 2002, an operation was
performed with the patient in the right lateral
position and under general anesthesia, after the
stability of circulatory dynamics and respiratory
conditions had been confirmed. A 25-cm S-curved
skin incision was made in the left posterolateral
region, and the thorax was opened at the 5th and
9th intercostal spaces. The tumor was located in the
dorsal region of the thoracic cavity and was strongly
and fibrously adherent
pericardium, aorta, and diaphragm. The adhesion
was detached at the tumor capsule, and the tumor
operation time was 5 hours and 25 minutes, and the
blood loss was 1,026 mL. The tumor was 27 × 19 ×
11 cm in size and weighed 3.2 kg. The tumor
consisted of nodular lesions of various size, with a
mixture of yellowish, fat-like, hard, fibrous, and bone-
like regions. Histopathological examination showed a
well-differentiated region assumed to be lipoma; a
region composed of atypical adipocytes, suggesting
occupying most ofthe
formation and a chondrosarcoma-like region were
also noted (Fig. 3b). On the basis of the above
findings, the tumor was diagnosed as a malignant
Hypoventilation of the left lower lobe due to
compression resolved immediately after surgery,
and the lobe was almost completely dilated. The
postoperative course was uneventful, and the patient
was discharged on day 12 after surgery.
In February 2006, 3 years and 6 months after
surgery, an abnormal shadow was noted on chest X-
ray examination during follow-up at the outpatient
clinic, and the patient was re-admitted for thorough
tothe lower lobe,
S. Tanimura, et al
214J Nippon Med Sch 2008; 75 (4)
F i g . 3 H i s t o p a t h o l o g i c e x a mi n a t i o n s h o we d r e g i o n s
o f a ) l i p o s a r c o ma a n d b ) c h o n d r o s a r c o ma .
F i g . 4 C h e s t C T s h o wi n g a 7 - c m t u mo r o n t h e
r i g h t s i d e c o n s i s t i n g ma i n l y o f a f a t t y
c o mp o n e n t a n d i n c o n t a c t wi t h t h e 9 t h
t h o r a c i c v e r t e b r a ; a n d a 4 - c m p a r t i a l l y
c a l c i f i e d t u mo r o n t h e l e f t s i d e b e t we e n t h e
1 2 t h t h o r a c i c v e r t e b r a a n d t h e d i a p h r a g m.
examination and treatment. On chest CT, the tumor
was found to have recurred on both sides of the
mediastinum, in contact with the thoracic vertebrae
(Fig. 4). Surgery was performed first
recurrent tumor on the left side of the mediastinum.
A left lateral incision was made, and the thorax was
opened at the 7th intercostal space. No anterior
adhesion in the thoracic cavity or severe adhesion
around the tumor was noted; adhesion of the tumor
to the lower lobe, esophagus, and aorta was slight;
and no infiltration was noted. The adhesion was
detached at the tumor capsule, and the tumor was
completely excised. The operation time was 1 hour
and 35 minutes, and the blood loss was 47 mL.
tumor was mostlyfibrosarcoma
Surgery for the tumor of the right side was
performed 1 month later. A posterolateral incision
was made on the right side, and the thorax was
opened at the 6th intercostal space. No adhesion was
present in the thoracic cavity, and the border of the
tumor was clear without infiltration. The tumor was
detached in the capsular region and completely
excised. The operation time was 1 hour and 45
tumor wasmostly liposarcoma
fibrosarcoma, but no
chondrosarcoma component was present.
The tumor had not recurred by 1 year and 8
months after surgery.
malignant tumor composed of two or more types of
mesenchymoma in 19481. Malignant mesenchymoma
frequently develops in the retroperitoneum and the
soft tissue of the lower limbs. The development of
such tumors in the heart, esophagus, liver, urinary
bladder and larynx has also been reported, but
development in the mediastinum is extremely rare2―7.
Tumors have been reported in persons ranging in
age from childhood to old age, but the incidence
tends to be highest in persons 60 years or older3.
Regarding the imaging
malignant mesenchymoma, CT and MRI images
reflect the histopathological heterogeneity of the
tumor. Mixed areas show the density of lipoma or
liposarcoma; differentiation into bone, cartilage and
Malignant Mesenchymoma in the Mediastinum
J Nippon Med Sch 2008; 75 (4) 215
Differentiation from malignant teratoid tumor is
possible based on the absence of a cystic structure.
Our case showed these imaging characteristics.
Histological diagnosis of the tumor is performed
with Stout’s definition.
sarcoma nor a fibrosarcoma-like region is counted as
a component, and these are not essential elements
for diagnosis of malignant mesenchymoma. Various
histological findings have
roughly be divided into the following two types: 1)
fibrosarcoma-like spindle cell components are often
leiomyosarcoma) and liposarcoma are mixed; and 2)
sarcoma components are apparently differentiated,
such as rhabdomyoma and liposarcoma, and are
accompanied by malignant cartilage and bone tissue
components. In our patient, the tumor consisted
mostly of fatty and fibrous components accompanied
by atypia, and partial atypical cartilage and bone
components were noted, suggesting classification
histopathological differentiation include liposarcoma.
In one reported case, well-differentiated liposarcoma
developed in the mediastinum in the first episode
mediastinum, with appearance of rhabdomyoma and
osteosarcoma and chondrosarcoma components5. In
such cases, differentiation
mesenchymoma is extremely difficult.
chemotherapy and radiotherapy may be ineffective.
In our patient, the tumor was strongly adherent to
the left lower lobe, pericardium, chest wall, aorta,
assumed to be thecapsule
organs. The hypoventilated lower lobe returned to
an almost original condition,
recovered without postoperative
although the tumor recurred on both sides of the
posterior mediastinum after 3 years and 6 months,
perhaps because of local recurrence of microscopic
residual tumor remaining in the mediastinal pleura.
A poor prognosis has been reported for malignant
mesenchymoma. In 8 femoral and retroperitoneal
cases described by Brady et al.3, the 2- and 3-year
survival rates were 75% and 37%, respectively, and
none of the patients survived for more than 5 years.
Because the tumor recurred 3 years and 6 months
after surgery in our patient, careful follow-up will be
Chemotherapy and radiotherapy were ineffective
for the soft parts of the sarcoma, including the
chemotherapy with doxorubicin plus ifosfamide and
dacarbazine has recently been reported9―11. Thus, a
radiotherapy, and chemotherapy may be useful for
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