The document discusses retroperitoneal masses. It notes that primary retroperitoneal masses originate in the retroperitoneum outside major organs. CT and MRI are important imaging modalities. Retroperitoneal masses can be solid or cystic neoplastic or non-neoplastic tumors. The majority are malignant. Common solid neoplastic masses include mesodermal tumors like liposarcomas, neurogenic tumors, and germ cell tumors. Imaging findings of common tumor types are described.

2. Retroperitoneal
masses
Dr. Ihusana Aminath
3rd year resident
NAMS, BIR HOSPITAL

3. • Primary retroperitoneal masses, which originate in
the retroperitoneum but outside the major
retroperitoneal organs, are uncommon.
• Divided primarily into solid and cystic masses, each
of which can be further subdivided into neoplastic
and non neoplastic masses.
• 70-80 % are malignant
• 0.1%-0.2% of all malignancies in the body.

4. Computed tomography (CT) and magnetic resonance (MR) imaging
Although CT is best for assessing calcification, MR imaging
has superior soft-tissue contrast, which is useful for staging and the
Ultrasonography (US) plays a relatively limited role in the evaluation

5. The differential diagnosis of retroperitoneal masses can be narro
required for definitive diagnosis.

6. The following are among the common signs:
a) The beak sign (positive when the mass causes the
edge of an adjacent organ to become beak shaped, meaning that th
b)The phantom organ sign (positive when a huge mass arises from
c) The embedded organ sign (positive when part of a hollow organ
d) The prominent feeding artery sign (particularly useful for hyperv

7. Specific diagnoses can be suggested with CT when the following ar
a) Calcifications (ganglioneuroma; malignant fibrohis
tiocytoma)
b) Adipose tissue (homogeneous: lipoma ; heterogeneous: liposarco
c) Necrotic areas (tumors with high grade malignancy
such as leiomyosarcoma
d) Hypervascularization (hemangioma, hemangioperi-
cytoma)
e) Areas of low homogeneous density (neurofibroma)

8. Signs that are specifically appreciable with MRI :
a) Target sign: central area with a low or intermediate
signal surrounded by a hyperintense ring in T2. Histologically it corre
b) Bowl of fruit sign: low intensity mosaic, intermediate and high sig

9. c) Whorled appearance: a linear or curvilinear structure appearing
d) Flow void: this is often seen in hemangiopericytoma, arterioveno
e) Speckled enhancement: this can be found in T1WI after CM and

10. • The retroperitoneum extends from the
diaphragm superiorly to the pelvis inferiorly
and is situated between the posterior parietal
peritoneum anteriorly and the tranversalis
fascia posteriorly.
• The retroperitneum is broadly divided into
the anterior and posterior pararenal
,perirenal and great vessel spaces.

11. • Insert retro picture

12. • Classification tables

13. • Classification tables

14. • Classification tables

15. Solid Neoplastic Masses
• Broadly divided into four groups:
a) Mesodermal neoplasms
b) Neurogenic tumors
c) Germ cell , sex cord and stromal tumors
d) Lymphoid and hematologic neoplasm

16. Mesodermal neoplasms
• Most of the retroperitneal neplasm are of mesodermal origin , with
liposarcomas ,leiomyosarcomas and malignant fibrous
histiocytomas making up more than 80 % of these tumors.
• Commonly seen in the 5th and 6th decades of life.
• They are large at the time of clinical presentation and often involve
adjacent structures
• Compression of adjacent organs causes formation of
pseudocapsules
• The recurrent rate is high.
• Metastases to liver,lung,bones and brain.

17. Liposarcoma
• Liposarcoma is the most common ( 33 % ) primary
retroperitoneal sarcoma.
• Liposarcoma is usually large ( average diameter >
20 cm ) ,slow growing tumor.
• It is predominantly hypo attenuating lesion on CT
because of its fat content.
• On MRI ,fat signal intensity is followed.

18. • The appearence of
liposarcoma maybe
similar to that of a
lipoma, but liposarcoma
has thicker ,irregular and
nodular septa that shows
enhancement after
contrast material
administration.

19. • Occasionally , a portion of the well - differentiated liposarcoma
undergoes histological dedifferentiation and becomes more
aggressive and metastatic eventually carries a worse prognosis
• CT & MRI imaging ,the dedifferentiated tumors are depicted as
heterogenous tumours with both fat and solid components and
shows lack of clear delineation between solid and fat components
• Calcification is seen in 30 % cases and is an important sign of
dedifferentiation.
• Variable signal intensity and enhancement of the solid portion
maybe seen.

20. Leiomyosarcoma
• Leiomyosarcoma is the second most common ( 28 % )
primary retroperitoneal sarcoma.
• It arises from retroperitoneal smooth muscle tissue ,
blood vessels or wolffian duct remnants.
• It can grow to a large mass ( > 10 cm ) before
compromising adjacent organs and precipitating clinical
symptoms such as venous thrombosis.
• Most common in women in the 5th to 6th decades.
• Predominantly extravascular ( 62 % ) or intravascular ( 5%
) also it can be a combination of extra and intravascular
components ( 33 % )

21. • On CT scan ,small
tumors can be
homogenously solid,
but large tumors
have extensive areas
of necrosis and
occasional
hemorrhage.

22. • MRI shows intermediate to low signal intensity on
T1WI and intermediate signal intensity on T2WI
,depending on the amount of necrosis.
• Mixed signal intensity and fluid debris level can be
seen in hemorrhagic lesions.
• The presence of extensive necrosis in a
reteroperitoneal mass, with contagious
involvement of vessel is highly suggestive of
leimoyosarcoma.
• Metastasis to the liver,lungs or lymphnodes occurs
late in the course of the disease.

23. • Approximately 6% of
leiomyosarcoma arise
from the IVC
• Most of these tumors
have a large
extravascular component
that makes it difficult to
distinguish from a
secondary involvement
of the IVC .

24. • The most commonly effected location is the segment
between the diaphragm and renal veins.
• Tumor involving the superior segment of the IVC (
above the hepatic vein ) may manifest with Budd-Chiari
syndrome.
• The middle segment (between the hepatic and renal
veins) manifest with right upper quadrant pain
,tenderness or with nephrotic syndrome.
• The inferior segment ( below the renal veins ) manifest
with pain and lower extremity oedema.

25. • MRI typically shows an intraluminal intermediate signal
intensity mass on T1WI and T2WI , with contrast
enhancement.
• The differential diagnosis includes benign thrombus
,angiosarcoma and a tumor extending into the IVC from
adjacent organs.
• While benign bland thrombus does not show contrast
enhancement,lieomyosarcoma of the IVC enhances on both early
and delayed ( 10 min ) contrast enhanced images and causes more
expansion of the IVC.
• Tumors from the middle segment of the IVC has a
better prognosis than those from other IVC segment.

26. Malignant Fibrous Histiocytoma
• It is the third most common retroperitoneal sarcoma (
19 %) and over all is the most common soft tissue
sarcoma in the body
• It arises from primitive mesenchymal elements and 15 %
of these tumors occur in the retroperitoneum.
• CT and MRI appearances are nonspecific and
demonstrate a large, infiltrating and heterogeneously
enhancing soft tissue mass with areas of necrosis and
haemorrhage and with invasion of adjacent organs.

27. • Variable patterns of
calcification can be
seen ( 7%-20% of
cases ) in the
peripheral of these
tumors
• The presence of
calcification may help
to distinguish
malignant
histiocytoma from
leiomyosarcoma.

28. Less common sarcoma -
Rhabdomyosarcoma
• It has bimodal distribution in the paediatric population,
peaks at 7 years and at adolescence.
• CT / MRI shows a mass lesion with areas of
calcification,necrosis and heterogenous enhancement.
• Occasionally , high flow
blood vessels maybe seen.
• Metastasis occurs in 10-20
% of cases because of
lymphatics or
hematogeneous spread.

29. Angiosarcoma
Angiosarcoma is a malignant tumor of endothelial and mesenchym
CT or MR imaging shows an enhancing mass expanding the involve
MR imaging may show high signal intensity on
T2WI , that is due to tumor necrosis and the presence of methemo

31. Angiomyolipoma
• It has varying amounts of blood vessels,smooth muscle cells
and adipose tissues.
• Commonly seen in females and associated with tuberous
sclerosis.
• Occurs in younger age group ( 25-35 years)
• Common loction is kidneys but occasionally seen in
retroperitoneum ,solid organs or skin.
• CT/MRI of angiomyolipoma ,small tumors are homogenbous
and large tumors area heterogenous soft tissue mass that
typically contain a large amount of macroscopic fat and
heterogenous enhancing vascular soft tissue.

32. • Enlarged vessels coursing through the lesion
,aneurysm and associated hemorrhage area
features that enable to distinguish
angiomyolipoma from liposarcoma
• Insert picture

35. Desmoid tumors
• Fibromatosis is a group of conditions that arise from musculoaponeurotic structures an
• Fibromatosis can be either superficial or deep.
• Desmoid tumor (deep fibromatosis, aggressive fibromatosis, well-differentiated fibrosa
• Desmoid tumor can be sporadic or associated with familial polyposis coli and Gardner s
• It is hormonally responsive and dependent on estrogen.
• This tumor is more common in females,from puberty to 40 years, with a peak in occurr
• Histologically, desmoid tumor is composed of well-differentiated
elongated uniform spindle cells, which are separated by collagen.

36. The imaging appearance of a desmoid tumor depends on the tissue composition (sp
At MR imaging, early-stage lesions are cellular and have high signal intensity on
T2-weighted images; but with loss of cellularity and deposition of collagen, the lesio
Hypo intense tracks may also be seen that are due to dense collagen bands.
Moderate to marked contrast enhancement is demonstrated on contrast enhanced
Deep desmoid tumor grows rapidly, is more aggressive, and is prone to recur (50%),

38. Neurogenic tumors
• Neurogenic tumours constitute of 10-20 % of
primary retroperitoneum tumours.
• Compared with the mesenchymal
tumors,neurogenic tumors occur in younger
age group ,more likely to be benign and better
prognosis

39. Neurogenic tumors originates from :
• 1. nerve sheath (
schwannoma,neurofibroma,neurofibromatosis
, malignant nerve sheath tumors )
• 2. ganglionic cells (
ganglioneuroma,ganglioneuroblastoma
,neuroblastoma)
• 3. Paraganglionic cells
(paraganglioma,pheochromocytoma )

40. Neurogenic tumors are commonly seen:
• Along the smpathetic ganglia,which are
located in the paraspinal region.
• In the adrenal medulla or the organs of
zuckerkandl (paraortic bodies ).

41. schwannoma
• Schwannoma or neurilemoma , is a benign tumour
that arises from the perineural sheath of Schwann (
neurilemma)
• It accounts for 6% of retroperitoneal neoplasm and
more common than neurofibroma.
• Asymptomatic.
• Females ( 2:1 )
• 20-50 year age group

42. • On CT ,small schwannomas are
round, well defined and
homogenous. If large ,shows
heterogenous in appearance.
• Calcifications can be
mottled,punctate or curvilinear
• The nerve of origin is often
difficult to identify.
• On post contrast study the
schwannomas show variable
homogenous or heterogenous
enhancement.

43. Neurofibroma
• Benign nerve sheath tumor that can occur as an
isolated ( 90%) or as part of type I
neurofibromatosis.
• Approximately 30% of solitary tumors and 100 % of
multiple tumors or plexiform neurofibromas are
associated with type I neurofibromatosis.
• Common in men of age 20- 40 years.

44. • On CT neurofibroma is
depicted as a well
defined round
homogeneously hypo
attenuating lesion ( 20-
25 HU ) because of the
presence of lipid –rich
Schwann cells and
adipocytes and
entrapment of adjacent
fat. On post contrast
study ,it shows
homogenous
enhancement.

45. • Tumors involving the
neural foramen have a
dumbells shape with
expansion of the
foramina or vertebral
body scalloping
• Plexiform neurofibroma
is seen as a large
extensive infiltrating
mass.

46. Malignant nerve sheath tumor
• Malignant nerve sheath tumor include malignant schwannoma
,neurogenic sarcoma and neurofibrosarcoma.
• Progressive enlargement , pain , irregular margins, heterogenous
nature and infiltration into adjacent soft tissues are suggestive of
malignancy especially when associated with type I
neurofibromatosis.

47. Ganglioneuroma
• Rare benign tumor that arises from the sympathetic ganglia
• The retroperitoneum ( 32%-52% of cases) and mediastinum (
39% -43% of cases) are the most common sites for
ganglioneuroma, followed by the cervical region ( 8%-9% of
cases )
• CT shows circumscribed lobulated hypoattenuating mass
that may surround a blood vessel without narrowing the
lumen.
• Discrete punctuate calcifications are seen in 20%-30%.

48. Ganglioneuroblastoma and neuroblastoma
• Ganglioneuroblastoma is an intermediate
grade tumor that has elements of benign
ganglioneuroma and malignant neuroblastoma
• It is a pediatric tumor occurring in 2-4 year age
group
• Imaging appearances vary,it can be solid or
cystic with solid components.

49. • Neuroblastoma is malignant and is more commonly seen in
males and in the 1st decade of life.
• 2/3rd of neuroblastomas are located in the adrenal gland
and the remaining neuroblastoma occur along the
paravertebral sympathetic chain.
• On CT / MRI imaging,neuroblastoma is irregular ,lobulated
and heterogenous and shows coarse amorphous
calcifications with variable contrast enhancement.
• It also shows invasion of adjacent organs and
enhancement of vessels with luminal compression.
• As many as 70% of patients have metastatic disease at the
time of diagnosis.

50. Paraganglioma
( Extraadrenal pheochromocytoma)
• Tumors that arise from the chromaffin cells of the adrenal
medulla are called pheochromocytomas, and those that arise in
an extraadrenal location ( 10%) are referred to as
paragangliomas.
• Paraganglioma is commonly
seen in the 3rd to 4th
decades with no sex
predilection.
• In the retroperitoneum ,
the most common site for
the paraganglioma is the
organs of
zuckerkandl,which are
located anterior to the
aorta at the level of the
origin of the inferior
mesenteric artery.

51. CT:
• Large well defined lobular tumor with areas of haemorrhage and
necrosis.
• Punctate calcifications is seen in 15% of cases and a fluid-fluid level
can be seen that is due to haemorrhage.
• Because of the hypervascular nature of paraganglioma,intense
contrast enhancement is seen.
MRI:
• Signal voids can be seen with T1W spin echo sequences
• Variable signal intensity is seen on T2WI
• Although paraganglioma maybe “ bright” , the tumor is usually
complex and heterogenous ( because of haemorrhage )

53. Germ cell , sex cord and stromal cell tumors
primary extragonadal germ cell tumors
• Histopathologically these tumors can be seminomas or non seminomatous
germ cell tumors, which include embryonal carcinoma,yolk sac tumor
,choriocarcinoma ,teratoma and mixed germ cell tumors
• The retroperitoneum is the second most common site of extra gonadal
germ cell tumor after the mediastium.
• Extragonadal germ cell tumor is often seen in or near the midline ,
especially between the T6 and S2 vertebrae.
• A midline mass is more suggestive of a primary extragonadal germ cell
tumor than of metastasis.
• On CT and MRI , the findings of primary extragonadal germ cell tumors are
non specific.

54. • Non seminomatous germ cell tumors are depicted as
heterogenous tumors with area of hemorrhage , necrosis
and heterogenous enhancement.

55. Teratoma
• A germ cell tumor that originates from pluripotent
germ cells that have been interrupted in their normal
migration for the genital ridge.
• Less than 10 % of teratomas are found in the
retroperitoneum.
• It is the third most common tumor in the
retroperitoneum in children after neuroblastoma and
wilm’s tumor.
• Commonly seen in females with a bimodal age
distribution ( <6 months and early adulthood )

56. • Mature teratomas are predominantly cystic.
Calcifcations and fat can be seen. A fat-fluid
(sebum) level and chemical shift between fat
and fluid are pathognomic.
Axial CT image of a
21 yr old woman
woman shows a
well defined
heterogenous
mass that
demonstrate fat
and teeth

57. Primary sex cord stromal tumors
• Extraovarian primary sex cord stromal tumor is more
commonly seen in the pelvis along the broad ligament
or fallopian tubes.
• Less commonly seen in the retroperitoneum or
adrenal glands.
• Most of these tumors are granulosa cell tumors.
• The imaging findings are non specific
• CT and MRI show heterogenous solid tumors with
heterogenous enhancement.

59. Lymphoid Neoplasms
Lymphoma:
• Most common retroperitoneal malignancy, accounting for
33% of these cases
• CT: shows a well defined homogenous mass, with mild
homogenous contrast enhancement , that spreads between
normal structures without compression them.
• The aorta and IVC can be displaced anteriorly , producing the
“floating aorta” or” CT angiogram” sign.
• Calcification and necrosis are unusual before therapy.

61. Solid non neoplastic masses
1. Pseudotumoral lipomatosis
2. Retroperitoneal fibrosis
3.Erdheim-chester disease
4.Extramedullary hematopoiesis.

62. Lipomatosis
• Lipomatosis is a benign metaplastic overgrowth of mature
unencapsulated white fat.
• Commonly seen in the pelvis and along the perirectal and
perivescular spaces.
• Less commonly seen in reteroperitoenum.
• CT& MRI : shows excess fat in the pelvis crowding the
anatomic structures with few fibrous tissue strands without
evidence of soft tissue mass or enhancement.

63. • A pear shaped bladder is produced by symmetric
compression and displacement of the bladder caused
by pelvic lipomatosis
• The lower portion of the ureters maybe pinched
medially, with resultant hydroureteronephrosis.

64. Reteroperitoneal fibrosis
• Uncommon collagen vascular disease of unknown cause
that can mimic retroperitoneal tumor.
• Typically idiopathic ( > 70 % of cases ) and is likely
autoimmune in origin.
• It can be secondary to
drugs,malignancy,hemorrahge,inflammatory conditions
,infection,radiation,chemotherapy,renal trauma and
amyloidosis.
• More common in males ( 3:1).
• Age: 40-60 years age group.

65. • CT : Irregular plaque like soft tissue mass in the
retroperitoneum,located around the aortic bifurcation
and extending along the iliac arteries and involving the
ureters,duodenum,pancreas and spleen/.
• It does not displace the aorta and IVC anteriorly , as
lymphoma or metastatic node often do ,but causes
tethering of these structures to the underlying vertebrae.

66. • Avid enhancement is seen in the active stages of
retroperitoneal fibrosis with little or no
enhancement in the chronic phase.
• MRI : High signal intensity on T2WI in the acute
phase of the disease, with early contrast
enhancement.
• Shows low signal intensity in the chronic
fibrosing phase with delayed enhancement.

67. Erdheim – chester disease
• It is a rare non- langerhans form of histiocytosis of
unknown origin.
• Extraskeletal lesions are seen in 50% of cases, with
retroperitoneal involvement seen in 1/3rd.
• Radiography shows
characteristics bilateral
symmetric osteosclerosis of
the metaphyseal diaphyseal
region of the long bones, with
sparing of the epiphysis and
lesser involvement of the flat
bones and axial skeleton.

68. • Retroperitoneal involvement with Erdheim-chester
disease characteristically produced a soft tissue rind
of fibrous perinephritis surrounding the kidneys and
ureters ,which can result in renal failure.

69. Extramedullary hematopoiesis
• seen in hemoglobinopathies,myelofibrosis,leukemia,lymphoma
and carcinoma.
• The typical CT appearance is hyper or isoattenuating round or
lobulated masses in the paravertebral region with or without
macroscopic fat.

70. • The MRI appearance is variable:
• Low signal intensity can be seen on T1WI and
T2WI because of the red marrow or hemosiderin
content.
• High signal intensity maybe found on T1WI and
T2WI because of fatty tissue.
• Enhancement is variable and often mild and
there is no associated bone destruction or
calcification.

71. • Insert table…

72. Cystic neoplastic masses
cystic change in solid neoplasms.
• Cystic changes may develop in solid lesions such as
paragangliomas and neurilemomas
• Cytic teratoma.
• CT shows a complex cystic mass with areas of fat and
calcification.
Lymphangioma:
• Lymphangioma is a developmental malformation that is
caused by failure of communication of reteroperitoneal
lymphatics tissue with the main lymphatic vessels.

73. Lymphangoima
• It can be seen in perirenal ,
pararenal or pelvic
extraperitoneal spaces and can
involve more than one
compartment.
• CT scan shows large thin walled
unilocular or multilocular cystic
mass with attenuation values
ranging from that of fat (
caused by chyle) to that of fluid
• Calcification is rarely seen .

74. • An elongated shape with involvement of
multiple compartments are salient features of
lymphangiomas , particularly those prone to
recurrence.
• The occurrence of septa,compression of
intestinal loops and lack of fluid in dependant
recesses and mesenteric leaves differentiate
lymphangioma from ascites.

75. Mucinous cystadenoma is a rare primary epithelial
retroperitoneal tumor that is believed to arise:
(a) secondary to invagination of peritoneal mesothelium with
subsequent mucinous metaplasia and
cyst formation,
(b) as a result of ectopic ovarian tissue,
(c) from a teratoma with single mucinous cell lineage, or
(d) from remnants of the embryonic urogenital apparatus.
Asymptomatic and is seen in women with normal ovaries.
Histologically, mucinous cystadenoma
has a single layer of tall columnar epithelial cells.
Mucinous cystadenoma

76. CT and MR imaging show a well-defined unilocular homogeneous cystic mass
This cyst requires surgical resection because of the risk of malignant transformation
Mucinous cystadenoma of the retroperitoneum in a 39-year-old woman.
Axial CT image of the
abdomen shows that a nonspecific well-defined unilocular simple cyst
(arrow) in the right retroperitoneal space
is displacing the colon anteriorly

77. Cystic nonneoplastic masses
Hematoma
• Reteroperitnoeal hematoma can have a variable imaging
appearance ,depending on its stage.
• Acute and subacute hematoma have heterogenous high
attenuation on CT and maybe hyperintense on T1WI and
T2WI .
• Chronic hematoma have low attenuation on CT images and
high signal intensity on MRI because of hemosiderin
deposition.

78. Retroperitoneal hematoma in a 51-year-old man who had undergone bone marrow biopsy. Co

79. Urinoma
• A well defined cystic lesion seen in retroperitoneum
, more common in the perirenal space.
• CT shows a well defined fluid collection, with
progressively increasing attenuation caused by
contrast enhanced urine entering the urinoma.

80. Urinoma in a 42-year-old man who had been in a motor vehicle accident. (a) Axial contrast-en
CT image obtained after the accident shows renal injury, with a hematoma (arrowhead) poste
collection (arrows) in the right anterior pararenal space. (b) Delayed axial contrast-enhanced C
the hematoma (arrowhead) and now shows the fluid collection filling with contrast material (a
the kidneys, a finding that indicates that this is a urinoma

81. Pancreatic pseudocyst
• It is a collection of pancreatic fluid that occurs secondary
to acute pancreatitis
• CT shows a well defined round or oval fluid collection
with enhancing wall.
Pancreatic pseudocyst in a 37-year-old
man with acute pancreatitis. Axial CT
image shows
edema (curved arrow) in the
peripancreatic region
and a unilocular cystic collection
(straight arrow) in the left anterior
pararenal space, a finding that is
consistent with a pancreatic
pseudocyst. Analysis of the fluid
obtained at aspiration of the cyst
revealed amylase in the cystic
collection.

82. Diagnostic clues for retroperitoneal mass

85. Conclusions
Retroperitoneal masses can arise from various
tissues and are a diverse group, including some
rare neoplasms.
CT and MR imaging are valuable in the evaluation of retroperitoneal m
Although a specific diagnosis might be difficult to determine because o
in narrowing the differential diagnosis.

86. Thank you
and
happy new

87. References.
• Textbook of Radiology and imaging ,david sutton
• CT and MRI of the whole body - Haaga .
• RSNA article.