2014, Volume 30, Number 3, Page(s) 215-219
Myopericytoma of the Liver Hilus: A Case Report
Amedeo FERLOSIO1, Tommaso Maria MANZIA2, Lucia ANEMONA1, Giuseppe TISONE2, Augusto ORLANDI1
1Department of Biomedicine and Prevention, Anatomic Pathology Institute, Tor Vergata University of Rome, ROME, ITALY
2Department of Experimental Medicine and Surgery, Transplantation Surgery, ROME ITALY
Keywords: Smooth muscle, Liver, Differential diagnosis
Pericytic tumours is a new category recently introduced in soft
tissue pathology describing those entities sharing evidence of myoid
differentiation and a tendency of spindle or more rounded cells
to grow in a perivascular fashion. The great majority of pericytic
tumours are benign but recurrence has been described as well as
very rare malignant cases with an aggressive behaviour. Although
pericytic tumours arise most commonly in the subcutaneous tissue
of distal extremities in middle age patients, additional cases have been
recently described in many other organs. Here we describe a case of a
57-year-old man with an 8.5 cm mass of the liver hilus diagnosed as
myopericytoma, with particular reference to its biological potential
and differential diagnosis. It is important for the pathologists to take
this diagnosis into consideration as well for a better management of
In the most recent WHO classification of soft tissue tumours,
the category named “pericytic (perivascular) tumours” has
. Previously, Requena et al. introduced
the term “myopericytoma” as an alternative designation for
solitary myofibroma, based on the supposed myopericytic
differentiation of the tumour2
. The term “myopericytoma”
encompasses a morphological spectrum of tumours
including glomus tumours, myofibromatosis and infantile
haemangiopericytoma, characterized by spindle cells with
contractile features and various arrangement around blood
. For this reason, the 2013 WHO classification
of soft tissue tumours introduced a category named
pericytic (perivascular) rather than vascular tumours1
The preferential site of involvement is subcutaneous tissue
of distal extremities. However, the increased recognition
of this entity showed wider sites of distribution, including
the proximal extremities, the neck and more rarely visceral
A 57-year-old male was admitted to hospital for
epigastric and right hypochondrium pain irradiated to
the chest. Past medical history was unremarkable. An
abdominal ultrasonography revealed gallstones and a
non-homogeneous solid lesion of 8.5 cm in diameter
located between the vena cava, aorta and hepatic hilum.
The laboratory tests showed neither liver dysfunction nor
markers level flare. Abdominal computerized tomography
revealed a hypodense parenchymal formation with a
homogeneous contrast enhancement (Figure 1
). The lesion
was 9.1 x 7.8 x 6.6 cm and involved the hepatic hilum,
the segment IV of the liver and the wall of the vena cava.
Endoscopic ultrasound-guided fine needle aspiration
biopsy did not provide sufficient material for a diagnosis.
An exploratory laparotomy was performed. Intraoperative
ultrasonography showed no involvement of adjacent
structures and the tumour was resected.
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|Figure 1: Abdominal Computerized Tomography: Scan image
showing hypodense formation (*) with a homogeneous contrast
enhancement involving the hepatic hilum, the segment IV of the
liver and the wall of the vena cava.
Macroscopically, the tumour was apparently well
capsulated, multi-lobated with a greyish cut surface and
hemorrhagic alternated to sclerotic areas. Microscopically,
a thin fibrous capsule incompletely delimitated the tumour
mass which was focally infiltrated the liver parenchyma
(Figure 2A). The tumour was mainly characterized by
“staghorn-like” vascular branching spaces surrounded by
spindle or epithelioid cells sometimes with abundant clear
cytoplasm embedded in a rich myxoid stroma (Figure 2BD).
Alternating, sclerotic areas and “solid growth” were
characterized by small vessels with fascicular arrangements
of neoplastic cells (Figure 2E-F). A multilayered concentric
proliferation of spindle cells with myoid features around
blood vessels was also observed (Figure 2G-H). Atypia and
mitosis were absent. Small areas of coagulative necrosis
were detected probably due to the previously performed
fine needle aspiration biopsy.
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|Figure 2: Microscopic findings: representative pictures showing A) The tumour focally infiltrating the liver parenchyma (**) (H&E;
x20) and B) Arising in close conjunction with major hilar vessels (H&E; x20), C,D) The characteristic “staghorn-like” branching vascular
spaces surrounded by spindle or epithelioid cells embedded in a myxoid stroma (H&E; x20 and H&E; x100), E,F) more solid areas with
fascicular elongated cells around small vessels (H&E; x100), and G,H) Characteristic concentric proliferation of spindle cells around
vessels (H&E; x100 and H&E; x400).
Immunohistochemical examination revealed that tumour
cells were α-smooth muscle actin positive (Figure 3A)
whereas CD34 (Figure 3B), CD31 (except for endothelial
cells covering the vascular spaces), CD99 and bcl-2
immonodetection were negative. The proliferative index
evaluated by Ki-67 nuclear positivity was lower than 1%
(Figure 3C). Concentric proliferations of spindle cells
around vessels were α-smooth muscle actin positive (Figure
3D). A diagnosis of myopericytoma was made. After 24
months, the patient is alive with no recurrence.
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|Figure 3: Immunohistochemical findings: tumour cells were A) α-smooth muscle actin positive (SMA; x20) and B) CD34 negative;
instead, endothelial cells covering the vascular spaces are CD34 positive, (CD34; x20) C) proliferative index evaluated by ki-67 expression
was very low (Ki-67; x20), D) detail of characteristic concentric proliferation of spindle cells around vessels highlighted by α-smooth
muscle actin positivity (SMA; x400).
“Pericytic tumours” are a new entity describing tumours
with perivascular myoid, myopericytic or myofibroblastic
differentiation enclosing the diagnosis of myopericytoma
and glomus tumour with its variants1-3
differences between these tumours are largely based
on cell morphology (more rounded or spindle cells),
growth pattern and the presence of a prominent vascular
component so representing a morphological continuum.
They arise most commonly in subcutaneous tissue of distal
extremities in middle aged patients; however, lesions can
arise at any age and anywhere1,4,6,7
. According to the
literature, just few cases of primary glomus tumour of
the liver have been described. Moreover, only one case of
myopericytoma of the liver are reported in a patient with
HIV infection and with multiple (intracranial, hepatic and
spinal epidural) tumours demonstrated histologically by
. This might depend more on its intrinsic rarity,
because until now this tumour has been enrolled among the
diagnosed cases of hemangioma or hemangiopericytoma.
The differential diagnosis of the pericytic tumours includes
both benign and malignant vascular neoplasms, the
so-called hemangiopericytoma and other fibroblastic/
myofibroblastic tumours, and finally true smooth muscle
tumours. Nowadays, the term hemangiopericytoma is
no more accepted and has been replaced with the term
“extrapleural fibrous tumour” for its fibroblastic origin3
The great majority of hemangiopericytoma expresses CD34
and CD99 antigens by immunohistochemistry, while only a
minority are bcl-2 and α-smooth muscle actin positive1
Hemangiomas are tumours characterized by proliferation
of vessels with scarcely intermingled mesenchymal
component and malignant vascular tumours show marked
. PEComas are tumours that display
both spindle and epithelioid cells with clear cytoplasm
resembling renal clear cell tumour and exhibiting atypia,
mitosis and necrosis with an infiltrative pattern1
Moreover, PEComa cells have a prevalent perivascular
pseudorosetting disposition around delicate vessels with
arborizing capillaries co-expressing neuromelanocytic
(such as HMB-45) and myocytic markers3
Although generally benign, pericytic tumours can recur
following excision. Recurrence is usually related to poor
circumscription of a lesion and so incomplete surgical
removal. Moreover, true malignant cases of perivascular
tumour with distant metastasis have been rarely described9.
Nevertheless, the histological aspect is not always predictive
of the clinical behaviour of some tumours, especially those
exhibiting “glomus-type” features9. High mitotic activity
(typical and atypical), the large tumour size and visceral
location are diagnostic criteria of malignancy1,9. When
a tumour does not fulfill all these criteria, the designation
“uncertain malignant potential” seems to be appropriate,
suggesting a possible more aggressive biological behavior.
The presence of a prominent vascularization suggests a
potential target for additional post-surgical therapy of more
In conclusion, it is important to take the possibility
of a pericytic tumour into consideration for a correct
differential diagnosis of primary liver neoplasms for a
better management of patient care.
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