Introduction:

Liposarcoma is a rare malignant tumour with a low incidence rate that accounts for less than 1 % of all malignancies.  According to the morphological characteristics and cytogenetics, sarcomas can be divided into liposarcomas, leiomyosarcomas and malignant fibrous histiocytomas among which, liposarcomas are the most common, accounting for 41% of all the sarcomas. Liposarcoma can occur in any region where fat is present. Approximately 30% occur in the retroperitoneal cavity. 35% originate from perirenal fat. Liposarcomas manifest as painless, progressively enlarging masses; thus, nearly half of retroperitoneal liposarcomas have diameters more than 20cm at the time of diagnosis. 

Primary retroperitoneal liposarcomas (PRPLS) occur mainly in patients aged 60-70 years, with no sex predominance. 

In the present case record,  we report on a  54 year old man with primary retroperitoneal liposarcoma. 

Clinical Profile:

A 54-year-old man came with complaints of pain in the left hypochondriac region for two months, insidious onset, non-progressive, associated with a bloating sensation. There is no history of vomiting, constipation, hematemesis or melena.  He had no history of trauma, weight loss, or fever. On examination, there was an ill-defined, hard swelling in the left hypochondriac region.

Radiological findings:

An AP radiograph of abdomen (Figure 1) shows a large,  ill-defined radiolucency of fat density in the left hypochondriac region displacing the bowel loops to the right.

 Fig1 : The AP radiograph of the abdomen shows an ill-defined radiolucency of fat density in the left hypochondriac region with displacement of bowel loops to the right.

A curvilinear ultrasound probe placed transversely in the hypogastric region showed a well defined,  heterogenous spherical mass  with few calcific foci. 

On the CECT  (Figure 2), there is a large, heterogenous fat density lesion with multiple septae, centered in the left retroperitoneal space. It extends medially to involve the prevascular space and the left psoas muscle. The lesion displaces the descending colon and small bowel loops anteriorly.

There is a well circumscribed,  heterogeneously enhancing round to oval soft tissue component with amorphous calcifications.

Fig 2  Plain, venous, and excretory phase axial and coronal CT scans of the abdomen show a  large 13x14x20cm (APXTRXCC) heterogenous lesion of fat density with multiple thin septae in the left retroperitoneal space. There is a well circumscribed, heterogeneously,  enhancing round soft tissue component measuring about 6 cm in diameter with amorphous calcification

On MRI, the lesion shows a large, ill-defined fat intensity lesion with multiple enhancing septation involving the left perirenal, anterior and posterior pararenal and left paracolic region. Medially,  the lesion extends to the preaortic and left paraaortic region. Anteriorly it causes  anterior displacement of descending colon and small bowel loop. Postero-medially there is involvement of the left psoas and quadratus lumborum muscles. Posterolaterally it is limited by the posterior pararenal and lateral conal fascia that is thickened. Inferiorly, the lesion surrounds the inferior pole of the left kidney with mild anterior displacement. Anteriorly,  the above lesion shows a large heterogeneously enhancing soft tissue component. Another small enhancing soft tissue component is seen inferior to the lower pole of the left kidney.

Fig. 3  The MRI shows large, ill defined, T1/T2 fat intensity lesion with multiple enhancing septation involving the left perirenal, anterior and posterior pararenal and left paracolic region Anteriorly it shows a heterogeneously enhancing soft tissue component

Radiological diagnosis:  

Primary retroperitoneal liposarcoma.

Pathological diagnosis:

 Primary retroperitoneal liposarcoma.

Final diagnosis: 

Primary retroperitoneal liposarcoma.

Treatment:

 The patient will undergo surgery to excise the mass.

 Timeline:     

Discussion

Liposarcoma originates from primitive mesenchymal cells and is composed mainly of adipocytes (1).  Liposarcomas often occur in the peritoneum, limbs, arms, and abdomen, and often invade deep soft tissues. (2a,b) Liposarcomas can be divided into five types pathologically: Highly differentiated, myxoid, polymorphic, round cell, and dedifferentiated. (3) . The prognosis of well-differentiated and myxoid liposarcomas is good. Most PRPLSs are easy to define, with an intact envelope that consists of a thin layer of flat tumor cells formed by tumor growth pressure. The tumor usually has distinct lobes, and each lobe is round or oval (4).

PRPLS, which occurs mainly in patients aged 60 to 70 years, is rare and without obvious symptoms in the early stage. Accurate diagnosis and complete resection are vital for the treatment of PRPLS. 

PRPLS has no obvious symptoms in the early stage, and a prominent feature is a huge abdominal mass with mild symptoms.(5,6) Similarly, retroperitoneal uterine leiomyoma also presents with non-specific symptoms, but patients with these tumors always experience pain during intercourse. (7) When diagnosed, PRPLS is often in the late stage, and the corresponding symptoms appear only when the adjacent organs are compressed or when tumors gradually increase in size. (8a,b) When the gastrointestinal tract is compressed, patients may feel fullness, anorexia, nausea, vomiting, diarrhea, abdominal pain, bloating, and pain related to constipation or defecation pain.(9) In addition, pressure on the kidney may cause hydronephrosis, and pressure on the bladder may cause frequent urination and urgency. (10a,b) Pressure into the chest from a large tumor may lead to breathing difficulties. (11a,b) 

Ultrasonography, CT, and magnetic resonance imaging (MRI) are especially important because the early clinical signs of liposarcoma are not obvious. Ultrasonography is used mainly to determine the size and number of tumors and has the advantages of non-invasiveness and low cost. CT is often the first auxiliary examination for PRPLS. CT has a certain value in judging the pathological type and malignant degree of PRPLS, but confirming these features depends mainly on the histological components of the tumor. (12a,b) Recent improvements in CT have led to higher resolution and clear images showing the size, location, and scope of liposarcomas and their relationship with surrounding organs. MRI can identify soft tissue diseases with important diagnostic significance for tumor invasion of structures, such as the abdominal aorta or inferior vena cava.

Complete surgical resection with negative margins is the main treatment for PRPLS. In a single-center study of 500 patients with PRPLS, patients who underwent complete surgical resection with negative margins had a median survival of 103 months. However, the median survival in patients who did not undergo complete resection was approximately only 18 months. (13) If it is difficult to remove the tumor completely in the advanced stage, tumor reduction surgery should still be performed to reduce the symptoms of compression, prolong survival time, and improve quality of life. (14) For patients with recurrent liposarcomas, reoperation should be performed.

Radiotherapy, including preoperatively, intraoperatively, and postoperatively, can be used to treat PRPLS to improve quality of life and tumor-free survival. (15a,b) Although well-differentiated and slow-growing PRPLS is relatively sensitive to radiotherapy, this modality is not a substitute for surgery. The combination of intraoperative radiotherapy, surgical resection, and postoperative external irradiation can control the patient's condition effectively. (16,17) However, it is still controversial whether adjuvant radiotherapy can improve the survival rate of PRPLS patients owing to the lack of sufficient clinical evidence.

Adjuvant or neoadjuvant chemotherapy is not a standard treatment method for PRPLS patients; however, it might be an option when the tumor is unresectable or insensitive to radiotherapy. (18,19) Although there are no specific chemotherapeutic drugs for liposarcoma, some combined chemotherapy agents possess significance for micrometastatic liposarcoma. (20ab,21) 

Radiotherapy and chemotherapy for PRPLS have not provided definitive effects. Therefore, tumors that recur post-surgery are recommended to be treated as soon as possible. Regular postoperative follow-up is required for PRPLS patients. Scientists should focus on the molecular mechanisms of liposarcoma to develop new targeted drugs for PRPLS. Surgery combined with targeted drugs, radiotherapy, or chemotherapy might reduce tumor recurrence and improve the prognosis of PRPLS patients.(22,23,24)

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