The retroperitoneal space contains lymphatics, connective tissue, and organs like the pancreas and kidneys. Retroperitoneal masses can be malignant tumors like lymphoma or sarcoma, or benign lesions such as lipoma or schwannoma. Computed tomography and magnetic resonance imaging are used to characterize the masses, and biopsy may help with diagnosis. Surgical resection is the primary treatment for retroperitoneal sarcoma and other localized tumors, while chemotherapy or radiation may help with advanced or unresectable cases.

1. Pathology
of
Retroperitoneal Mass

2. 

The retroperitoneal space is a potential space
extending posterior to the abdominopelvic cavity.
The tissue within this mixed potential and actual
space is composed of:
 Lymphatics and loose connective tissue.
 Organs that are partially or completely
retroperitoneal include:
•
•
•
•
Pancreas,
kidney,
Adrenal glands,
Ureters.
 Vascular structures:
• Aorta and inferior vena cava.
 Significant lumbar nerves
traverse the space.

3. Differential diagnosis of
retroperitoneal soft tissue mass
The term retroperitoneal tumour is at times confined to the lesions arising
from tissues (muscles, fat, fibrous tissue, lymph nodes, nerves and
developmental remnants) of this compartment but excluding origin from the
retroperitoneal organs.
Malignant lesions:
•
•
•
•
Lymphoma (most common)
Sarcoma (2nd most common)
GIST
Germ cell tumor
Desmoid tumors.
Benign lesions:
•
•
•
•
Lipoma
Peripheral nerve sheath tumor
Teratoma
Paraganglioma

4. Diagnostic Work-Up

Computed tomography (CT):

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Large lesions with fatty components causing mass effect
frequently represent liposarcomas.
Teratomas often have fat, fluid, and calcified components.
Paraspinal locations point to nerve sheath tumors or neurogenic
derivation .
Magnetic resonance imaging (MRI)
may demonstrate additional imaging
details to further classify the lesion.
CT-guided needle biopsy may be
performed as the initial means of
obtaining tissue for histologic
diagnosis

5. Retroperitoneal Sarcoma

Second most common malignant RPT.

Arise from: nonepithelial, extraskeletal tissues:
(fat, muscle, nerve and nerve sheath, blood vessels, other
connective tissues).

Incidence: 9,220 cases per year in the United
States.

Common types:


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Leiomyosarcoma,
Liposarcoma,
Fibrosarcoma.

6. ‫‪Retroperitoneal sarcoma‬‬
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7. Retroperitoneal sarcoma
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
Primary treatment of retroperitoneal soft tissue
sarcoma (STS) is to attempt a gross total
resection.

Criteria for unresectable tumors commonly
include major vessel invasion and spinal cord or
vertebral body involvement.

Resectability has been reported in recent series
to range from 65% to 85%.

8. Retroperitoneal sarcoma
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
Macroscopically positive margin is one the
most important prognostic features in
determining local control and survival.

Even after a complete excision of RPS, local
recurrence rates (33% to 77%) and overall survival
rates (35% to 63% 5-ys OS) are poor.

retrospective data demonstrate a decrease in
local failure with adjuvant radiation therapy.

The use of adjuvant and neoadjuvant
chemotherapy is not standard.

9. Retroperitoneal sarcoma
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Patients with unresectable disease:
• May benefit from a course of preoperative radiotherapy or
chemotherapy in attempt to shrink the tumor.
• Palliative debulking surgery may be offered.
Patients with metastatic disease:
 Solitary or limited metastases:
should be managed similarly to those with localized disease with
consideration for preoperative radiation therapy and/or chemotherapy,
metastasectomy, radiofrequency ablation. Chemotherapy may be
considered (most commonly, Doxorubicin-based regimens).
 Disseminated metastatic disease:
treated with palliative intent (chemotherapy, radiation therapy, palliative
surgery or best supportive care.)

10. GIST
gastrointestinal stromal tumour

These tumors that derive from the precursors of
the interstitial cells of Cajal may occur
anywhere in the GI tract, but most often from the
stomach and small intestine.

incidence is estimated to be approximately
1.5/100,000 per year.

Approximately 95% of GISTs are CD117 (c-KIT)
positive.

11. GIST
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 Surgery:
• Remains the only potentially curative treatment for
patients with localized GIST.
• Optimal surgery requests complete excision of the
tumor without rupture in order to avoid seeding of
tumor cells.
• No role in advanced or metastatic disease.
Imatinib (targeted therapy):
• Tyrosine kinase inhibitor of c-KIT.
• Adjuvant: in tumors > 3 cm, for 1 year.
• Upfront therapy: in advanced and metastatic cases.

12. Desmoid tumors

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
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(aggressive fibromatosis)
Rare, benign neoplasms.
Arise from muscle fascia, aponeuroses, tendons,
and scar tissue.
More commonly in females .
Associated with familial adenosis polyposis .
Tend to be locally aggressive and have a propensity
to recur locally after resection.
Treatment is complete resection with a 2-3 cm
margin.
Postoperative radiation therapy is used in cases
with an unresectable primary, after multiple local
recurrences.

13. Schwannomas

Most common benign tumors in the retroperitoneum.

Typically form large, well-circumscribed masses (may
display cystic degeneration, calcification, hemorrhage).

MRI is the recommended imaging study.

Not suggest CT-guided biopsy or fine-needle
aspiration for the diagnosis because of the risk of
hemorrhage as it is usually a highly vascular tumor.

Complete surgical resection with negative margins is
the treatment of choice.