Malaysian J Pathol 2016; 38(1) : 61 – 64
CASE REPORT
Solitary fibrous tumour of the chest wall
Norhafizah MOHTARRUDIN
MPath,
Zubaidah NOR HANIPAH*
MS,
and Noraini MOHD DUSA**
MPath
Departments of Pathology and *Surgery, Faculty of Medicine and Health Sciences, Universiti Putra
Malaysia, Selangor and **Department of Pathology, Hospital Kuala Lumpur, Kuala Lumpur, Malaysia
Abstract
Extrapleural solitary fibrous tumours (SFTs) are rare tumours characterized by patternless spindle
cells with haemangiopericytoma-like vascular spaces. Previously the tumours have been classified
as haemangiopericytoma, an entity that is now considered obsolete. We report a case of extrapleural
SFT arising in the soft tissue of the chest wall. The patient was a 31-year-old Malay lady
presenting with a mobile swelling of the right chest wall for more than five years. During excision
the tumour was noted to be well-circumscribed and yellowish in colour, giving an impression of
lipoma. Microscopically, the tumour had patternless architecture, characterized by hypocellular
and hypercellular areas. It was composed of uniform, spindle-shaped cells displaying oval nuclei,
inconspicuous nucleoli, pale cytoplasm and indistinct cell borders. The mitotic count was 2 per 10
HPF. Branching, medium-sized thin-walled blood vessels in a haemangiopericytomatous growth
pattern, some with hyalinised wall were identified. The neoplastic cells were immunoreactive to
CD99 and CD34 and were non-immunoreactive to Desmin, Smooth Muscle Actin, S100 protein and
EMA. We elucidate the challenges in diagnosing this tumour in this unusual location.
Keywords: extrapleural, solitary fibrous tumour, haemangiopericytoma, chest wall
INTRODUCTION
CASE REPORT
Solitary fibrous tumour (SFT) of the pleura
was first reported in 1931 by Klemperer and
Rabin.1 Although SFTs are mostly found in the
pleura, up to one third of the cases have been
reported in various extra pleural sites such as the
mediastinum, lungs, liver, upper respiratory tract
and peritoneum.2-4 Extra pleural SFTs arising
from the chest wall is extremely rare. From
the literature, only a few cases arising from the
anterior chest wall has been documented.5 In
such cases, there was preoperative diagnostic
dilemma, especially for the extra pleural tumours.
Therefore, radiological imaging such as computed
tomography or magnetic resonance imaging is
required prior to surgery.5 Even though SFTs
are mainly benign tumours, there has been
some evidence of aggressive behaviour, local
recurrence and distant metastasis long after
primary resection. Rarely malignant solitary
fibrous tumour has been reported. Therefore,
complete surgical excision is mandatory.
A 31-year-old Malay lady presented with a
swelling of the right chest wall for more than
five years. The swelling had slowly increased
in size and was painless. There was no history
of trauma. She is a known case of childhood
bronchial asthma and is on metered-dose inhaler
(MDI); 2 puffs daily. Her last attack was the
year before.
On examination, there was a mobile swelling
measuring 60 x 50 mm located in the lateral
right chest, anterior to the axillary line. The skin
overlying the swelling was smooth with presence
of two blood vessels. No pulsation was noted or
bruit heard on auscultation. The initial clinical
impression was haemangioma.
The patient was planned for excision biopsy.
Upon removal, the tumour was noted to be
well-circumscribed and yellowish in colour.
There were no vascular spaces or haemorrhagic
areas seen. Hence the intra- and post-operative
diagnosis was lipoma. The specimen was sent
to the Pathology Laboratory for histopathological
examination.
Address for correspondence: Dr Norhafizah bt Mohtarrudin, Department of Pathology, Faculty of Medicine and Health Sciences, Universiti Putra
Malaysia, 43400 UPM Serdang, Selangor, Malaysia. Email: [email protected]
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Malaysian J Pathol
April 2016
FIG. 1: Patternless architecture with hypocellular and hypercellular areas within myxoid to collagenous matrix.
(Hematoxylin & eosin stain, original x40)
Pathology
On gross examination, there was a wellcircumscribed, encapsulated tumour measuring
60x60x40 mm. Cut sections showed a whitish
lesion admixed with minimal yellowish fatty
tissues intersected into lobules by thin fibrous
septa.
Microscopically, the tumour had patternless
architecture; characterized by hypocellular
and hypercellular areas (Figure 1). It was
composed of uniform, spindle-shaped cells
displaying oval nuclei, inconspicuous nucleoli,
pale cytoplasm and indistinct cell borders. The
mitotic count was 2 per 10 HPF. Branching,
medium-sized thin-walled blood vessels in a
haemangiopericytomatous growth pattern, some
with hyalinised wall were identified (Figure 2).
It has a diverse background from myxoid
FIG. 2: Branching, medium-sized, thin-walled blood vessels in a haemangiopericytomatous growth pattern, some
with hyalinised wall. (Hematoxylin & eosin stain, x100)
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SOLITARY FIBROUS TUMOUR
FIG. 3: The neoplastic cells were immunoreactive to CD34. ( x100)
to collagenous matrix. Keloidal collagen
deposition was commonly seen. Mast cells and
lymphocytes and occasional vacuolated spaces
were found scattered in the background. There
was no necrosis or infiltrative margins. The
histopathological impression was a benign
spindle cell tumour. Immunohistochemistry study
was conducted to assist in the final diagnosis.
The neoplastic cells were immunoreactive to
CD99 and CD34 (Figure 3). They were nonimmunoreactive to Desmin, Smooth Muscle
Actin, S100 protein and EMA. The microscopical
and immunohistochemical findings were most in
keeping with a solitary fibrous tumour.
DISCUSSION
Solitary fibrous tumour (SFT) is a mesenchymal
tumour of fibroblastic type with prominent
haemangiopericytoma-like branching vascular
pattern resembling staghorn configuration.
Their cell of origin is still debated. In the
past, most SFT cases were diagnosed as
“hemangiopericytomas”.6
SFT is ubiquitous but most often arise in the
pleura. However extrapleural solitary fibrous
tumour (SFT) is rare. It represents less than 2% of
all soft tissue tumours.7 In our case it is located
at the chest wall that is rarely encountered.
Our patient presented with a painless and
slow growing tumour of more than 5 years.
These are typical presentations of most STFs
though there are no specific symptoms for these
tumours.6 SFTs are usually well-circumscribed,
whitish and multinodular intersected by fibrous
septae and measuring between 1 and 25 cm. In
our case, the presence of yellowish tissue has
led to an intraoperative diagnosis of lipoma.
Microscopically, a haemangiopericytomatous
vascular pattern is an important clue to the
diagnosis. Previously haemangiopericytoma
is considered as a diagnostic entity. Now it is
considered as a morphological vascular pattern
seen in some soft tissue tumours such as SFT and
synovial sarcoma. In a recent WHO classification
of soft tissues; hemangiopericytoma was
considered an obsolete entity. 6
The differential diagnosis of SFTs of soft
tissues is extensive as SFTs have patternless
pattern. Other characteristics are spindle cells
of variable cellularity separated by thick bands
of hyalinised collagen that divide the tumour
into multinodular areas that can be appreciated
macro- and microscopically.6
Malignant STFs are rare. However it is
important to assess evidence of cellular atypia,
necrosis and infiltrative margins. Malignant
STFs are usually hypercellular, with high mitotic
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counts (>4 per 10 HPF), exhibit cellular atypia,
tumour necrosis, and/or infiltrative margins.8
Adequate sampling of the necrotic areas and
margins are important to delineate the benign
and its malignant counterpart. Our case showed
none of the malignant features.
There are no distinctive immunohistochemical
or electron microscopical features in SFT. It
may be difficult to separate this tumour from
other spindle-cell tumours by hematoxylin-eosin
staining alone. Immunohistochemistry could
assist to exclude the possibility of epithelial,
neural, and myogenous differentiation. The
spindle cells of STFs are immunoreactive for
CD34 and CD99 as demonstrated in our case.9,10
The cells usually lack other immunodeterminants
for cytokeratin, S100 and Desmin.11
In view of the clinical diagnosis and
pathological features, the possibility of spindle
cell lipoma needs to be excluded. Spindle cell
lipoma may resemble fat-forming SFT. Both are
composed of spindle cells surrounded by thick
collagen and myxoid background. Hyalinised
vessels can also be seen. Important features to
differentiate between the two entities are typical
bland spindle cells and usual location in spindle
cell lipoma. Furthermore spindle cell lipoma
is usually negative for CD99.6,11 Besides that
synovial sarcoma that is usually immunoreactive
for cytokeratin, EMA and CD34 was also
excluded.11
The behaviour of SFT is unpredictable and
there is poor relationship between morphology
and outcome. Some “malignant” tumours
behave benign while some morphological
“benign” lesions behave aggressively. Substantial
number of patients developed local recurrence
or metastases. Local recurrence is significantly
higher in patients with positive resection margins.
Metastasis is significantly higher in patients with
tumour size >10 cm and high mitotic rates.8
En-bloc surgery is the recommended treatment
for both benign and malignant SFT.12 Malignant
SFT also needs regular oncological follow-up in
view of recurrence.
Prognosis is better for a well-circumscribed
tumour with no nuclear pleomorphism or
mitoses. In addition to the histological criteria
of malignancy, absence of sclerotic-hypocellular
areas and tumour size more than 10 mm have
been considered predictors of poor outcome. 5
In summary, chest wall SFT is extremely rare
with challenging diagnosis. Precise histological
diagnosis with immunohistochemical analysis is
important. Surgical excision is the recommended
treatment for this SFT.
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April 2016
ACKNOWLEDGEMENT
The authors would like to thank the Director
of Health Malaysia for permission to publish
this paper. The authors declare that there is no
conflict of interest to disclose.
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