Case of the week Details

• Axial arterial phase image depicting large retroperitoneal lesion with multiple enhancing septations (blue arrow) in left side of abdomen displacing adjacent organs (yellow arrow).
• Coronal image shows that the lesion occupies the abdomen near completely with predominant fat density. Solid enhancing component with calcific specks are seen (white arrow).
• Coronal image shows that the lesion occupies the abdomen near completely with predominant fat density. Solid enhancing component with calcific specks are seen (white arrow).
• Axial venous phase image at caudal level shows solid enhancing components within the lesion (blue arrows), and a  ventral hernia with fat and fluid within (red arrow).
• Patient underwent resection of the lesion followed by left hemicolectomy. Samples were sent for HPE.

RETROPERITONEAL LIPOSARCOMA (HPE:- Dedifferentiated variant)

DISCUSSION:

• Primary retroperitoneal sarcomas (RPS) represent around 10–16% of all sarcomas, with liposarcomas and leiomyosarcomas being the most common subtypes.
• RPS primarily present as large masses, progressively encasing adjacent structures, causing mass effect.
• Symptoms are commonly associated with displacement, compressive or obstructive phenomena, and include abdominal or back pain, urinary tract obstruction, edema of the lower limbs, nerve compression, and vague digestive symptoms.
• Recurrence - 45 to 49% within the first five years , 60 to 82% at 10 years after initial treatment. Lifelong surveillance is advised. 
• Nodal mets is rare and is a poor prognostic sign.
• Retroperitonel liposarcomas have 5 histological subtypes:
  • Well differentiated
  • Myxoid (myxoid has moer mucopolysacharides – T2 hyperintense)
  • Pleomorphic
  • Round cell
  • Dedifferentiated
• Often metastasize hematogenously.
• Calcifications are often present in dedifferentiated variant and implies poor prognosis.
• Role of radiologist is to rule out other conditions like adenocarcinoma, retroperitoneal fibrosis, lymphoma, paraganglioma etc (LPS mimics angiomyolipoma in having fat density).
• CECT helps to identify the origin, contents (fat, solid, calicific) and also mass effect over adjacent organs with complications if any (eg:- ureteric obstruction or vascular compromise).
• Within the lesion there could be thin septations (low grade) to heterogenous sold mass (high grade).
• MRI – myxoid components can show T2 hyperintensity. Delayed post contrast enhancement can be seen.

TREATMENT

• Surgery is mainstay.
• Resection margins must be clear, otherwise resulting in high rates of recurrence.

REFERENCES

• Mota MM, Bezerra RO, Garcia MR. Practical approach to primary retroperitoneal masses in adults. Radiologia brasileira. 2018 Nov 23;51:391-400.
• Porrello G, Cannella R, Randazzo A, Badalamenti G, Brancatelli G, Vernuccio F. CT and MR Imaging of Retroperitoneal Sarcomas: A Practical Guide for the Radiologist. Cancers (Basel). 2023 May 30;15(11):2985. doi: 10.3390/cancers15112985. PMID: 37296946; PMCID: PMC10252049.
• Craig WD, Fanburg-Smith JC, Henry LR, Guerrero R, Barton JH. Fat-containing lesions of the retroperitoneum: radiologic-pathologic correlation. Radiographics. 2009 Jan;29(1):261-90.

Dr THIMMANNA K.D
Consultant Radiologist
Manipal Hospital, Yeshwanthpur, Bengaluru.

Dr ANAGH VISHNU NARAYANAN
Radiology resident
Manipal Hospital, Yeshwanthpur, Bengaluru.