AJR 2005; 184:S67-S69
© American Roentgen Ray Society
Benign Omental Hemangiopericytoma Presenting with Hemoperitoneum: Radiologic Findings
Federico Crusco,
Marino Chiodi,
Fabrizio Pugliese,
Stefano Mosca,
Matthias Joachim Fischer and
Luciano Lupattelli
Department of Radiology, University of Perugia, Via Brunamonti 51,
Perugia 06122, Italy.
Received January 26, 2004;
accepted after revision April 16, 2004.
Address correspondence to F. Crusco
(fcrusco{at}sirm.org).
Introduction
Hemangiopericytoma is a rare perivascular tumor arising from the
pericytes of Zimmerman and occurs primarily in adults and rarely in children,
with no sex predilection. The most common sites of involvement are the lower
extremities, head, neck, and retroperitoneum; less frequently, it affects the
abdomen and pelvis. It usually appears as a well-circumscribed, solid
hypervascular mass; necrosis and hemorrhage indicate a malignant form. In both
benign and malignant cases, surgical removal is the primary treatment. To our
knowledge, only 11 cases of omental hemangiopericytoma have been reported in
the literature. We present a surgically confirmed case of omental bleeding
hemangiopericytoma presenting with hemoperitoneum.
Case Report
A 24-year-old man with a medical history of vague abdominal malaise was
admitted to our hospital for an acute onset of pain in the lower left
quadrant. Physical examination revealed mild tenderness to palpation in the
lower abdominal quadrant. Laboratory values showed mild anemia with a
hemoglobin level of 12.1 g/dL. The patient's serum chemistries, liver, and
renal function tests were normal. An abdominal sonogram was obtained and
revealed a 2.5 x 2 cm mass with a heterogeneous echo pattern in the
pelvic inlet, just behind the left rectus abdominal muscle and close to the
external iliac vessels. The mass was highly vascularized on color Doppler
sonography. A small amount of free intrabdominal fluid in the Douglas pouch
was also noted. On unenhanced MDCT (LightSpeed, GE Healthcare), the fluid
collection had high attenuation values (58 H), consistent with hemoperitoneum
(Fig. 1A). Contrast-enhanced CT
showed a well-defined mass without signs of local invasion, with centripetal
enhancement in the arterial phase and homogeneous and persistent enhancement
in the venous phase (Figs. 1B
and 1C). No calcifications were
noted. A vascular pedicle larger than 20 cm was included in the trabecular
connective tissue of the omentum, adjacent to the epigastric vessels. It was
formed by a feeding artery originating from the splenic artery at the level of
the splenic hilum with a parallel venous drainage
(Fig. 1D).
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Fig. 1A. —24-year-old man with abdominal pain in left lower quadrant
and mild anemia. Unenhanced MDCT scan shows soft-tissue, well-circumscribed
mass with small amount of free fluid in rectovesical pouch compatible with
hemoperitoneum.
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Fig. 1C. —24-year-old man with abdominal pain in left lower quadrant
and mild anemia. On contrast-enhanced CT scan, enhancement is homogeneous
during venous phase with same attenuation values as iliac vessels.
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Fig. 1D. —24-year-old man with abdominal pain in left lower quadrant
and mild anemia. Three-dimensional maximum-intensity-projection image shows
long vascular pedicle originating from splenic hilum included in omental
tissue adjacent to epigastric vessels.
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To better visualize the vascular pattern of the lesion, we performed a
selective and superselective celiac arteriography before surgery. The presence
of the mass with its unique splenic pedicle was confirmed, with no signs of
active bleeding (Fig. 1E).
Based on these findings, an omental hypervascular tumor of unknown origin was
suspected. Laparascopy revealed a solid, well-encapsulated, nonbleeding
intraperitoneal lesion attached to the free margin of the greater omentum. The
excised tumor had a red-brown appearance and a fleshy consistency. On the cut
surface, many vessels of various sizes were visible
(Fig. 1F). Histologic
examination confirmed the diagnosis of benign hemangiopericytoma with evidence
of an architectural pericytic pattern and a low mitotic rate.
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Fig. 1E. —24-year-old man with abdominal pain in left lower quadrant
and mild anemia. Angiogram shows dense accumulation of contrast medium owing
to filling of fine vessels early in arterial phase.
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Fig. 1F. —24-year-old man with abdominal pain in left lower quadrant
and mild anemia. Surgical specimen is oval-shaped, red-brown tumor with
soft-cut surface and periferical vascular spaces of varying size.
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Discussion
Definitive histologic diagnosis of hemangiopericytoma is based on an
architectural hypervascular pattern with pericytes surrounding anastomosing
vessels. A prominent mitotic rate (
4 mitotes/10 high power field),
hypercellularity with immature tumor cells, hemorrhagic areas, and necrosis
are indicative of malignant rather than benign lesions
[1]. Radiologic features of
omental hemangiopericytoma are nonspecific. Sonographic findings typically
include a mass with clearly defined margins and a heterogeneous echo pattern
that is highly vascularized on color Doppler sonography and a pedicle entering
the tumor and branching into large vessels
[2].
CT appearances were first presented by Alpern et al.
[3] in 1986 in a series of
seven patients. A large, well-demarcated soft-tissue mass without
calcification that does not invade adjacent organs is suggestive of the benign
form. The presence of cystic areas of low attenuation consistent with
necrosis, dystrophic calcifications, and invasion of the surrounding
structures indicate that the tumor is more likely to be malignant.
Contrast-enhanced CT shows a homogeneous, highly vascularized tumor.
Angiographic and microangiographic studies show that the hypervascular pattern
with homogeneous and centripetal opacification early in the arterial phase is
suggestive of hemangiopericytoma but is not specific
[4]. Angiography is helpful to
evaluate the feeding artery of the tumor and its venous drainage. In the
series reported by Goldman et al.
[5] of 17 retroperitoneal and
pelvic tumors, feeding blood vessels included the thoracic, lumbar, adrenal,
inferior mesenteric, celiac, hepatic, splenic, and the common external and
internal iliac arteries. In our case, a vascular pedicle larger than 20 cm was
derived from the splenic vessels. Because of the rich vascularity of the
lesion preoperatively, embolization may be considered to shrink the tumor and
minimize intraoperative hemorrhage.
To our knowledge, our report is the first that has shown a benign omental
hemangiopericytoma presenting with hemoperitoneum. We found that
hemoperitoneum was related to recent bleeding of the mass; an active
hemorrhage was excluded by arterial phase CT and arteriography. Although rare,
hemangiopericytoma is one of the most common primary tumors of the omentum and
should be considered in the differential diagnosis of soft-tissue masses
arising in this region, such as leiomyosarcomas, fibrosarcomas, spindle cell
sarcomas, liposarcomas, leiomyomas, and fibromas
[6]. The radiologic findings of
the neoplasm are nonspecific; however, hypervascularity of the lesion and the
presence of a vascular pedicle may help the clinician to narrow the diagnostic
possibilities. In particular, contrast-enhanced CT and angiography provide
important information for appropriate diagnosis and presurgical treatment
planning by showing the hypervascular nature with centripetal opacification,
the blood supply of the lesion, and its relationship with the surrounding
structures.
References
- Enzinger FM, Smith BH. Hemangiopericytoma: an analysis of 106
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- Bertolotto M, Cittadini G Jr, Crespi G, Perrone C, Pastorino R.
Hemangiopericytoma of the greater omentum: US and CT appearance.
Eur Radiol 1996;6:454
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- Alpern MB, Thorsen MK, Kellman GM, Pojunas K, Lawson TL. CT
appearance of hemangiopericytoma. J Comput Assist
Tomogr 1986;10:264
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- Angervall L, Kindblom LG, Nielsen JM, Stener B, Svendsen P.
Hemangiopericytoma: a clinicopathologic, angiographic and microangiographic
study. Cancer1978; 42:2412
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- Goldman SM, Davidson AJ, Neal J. Retroperitoneal and pelvic
hemangiopericytomas: clinical, radiologic and pathologic correlation.
Radiology1988; 168:13
-17[Abstract/Free Full Text]
- Ishida H, Ishida J. Primary tumours of the greater omentum.
Eur Radiol 1998;8:1598
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Introduction
Case Report
