Primary retroperitoneal liposarcoma (PRPLS) originates from soft tissue in the retroperitoneum and is rarely observed clinically[1-4]. Since the clinical symptoms are usually nonspecific and its anatomical location is the retroperitoneal space, reaching an early definitive diagnosis of PRPLS is usually difficult. Complete resection by surgery is the main mode of treatment for this disease. Owing to the complex pathology of this disease, the effectiveness of chemoradiotherapy is limited[7,8]. The prognosis of this disease depends on the pathological type; however, all types are linked to a high local recurrence rate[9,10]. Therefore, it is important to promptly detect the disease, administer appropriate treatment, and regularly monitor the disease progression after operation[10,11]. Herein, we report a case with multiple PRPLS managed at our hospital and review the currently literature on this disease.
A 64-year-old man was referred to the Department of General Surgery, Affiliated Hospital of Hebei University (Baoding, China) in July 2018, with a complaint of abdominal distension for 1 year.
History of present illness
Apart from abdominal distension, the patient was asymptomatic, without distinct medical, surgical, or medication history.
A physical examination revealed the presence of abdominal bulge with a flexible mass (dimensions: 24 cm × 20 cm) located in the abdomen. This mass had a regular shape, clear boundary, and was palpable with a rubbery medium-hard texture. There was no pain upon application of pressure on the mass.
The laboratory examinations, including the assessment of tumor markers (alpha fetoprotein, carcinoembryonic antigen, carbohydrate antigen (CA) 125, CA15-3, CA19-9, and CA72-4), as well as routine blood, urine, and stool tests, did not reveal abnormalities.
Ultrasound examination showed a solid hypoechoic mass (dimensions: 18.5 cm × 15.5 cm × 8.8 cm) in the right middle abdomen. The upper and lower margins reached the subcostal region, and the subumbilicus, respectively. The boundary was clear, the morphology was irregular, and the internal echo was not uniform. Marked echo interheterogenicity was observed in the center, and blood flow signals were detected around and within it through color Doppler flow imaging; in the lower abdomen, there were several echo groups with strong echo intensity, and the boundary was unclear. The dimensions of the largest mass in the right and left lower abdomen were approximately 8.3 cm × 5.0 cm and 7.9 cm × 4.4 cm, respectively; both had a vague boundary and an irregular shape (Figure 1).
Figure 1 Ultrasound examination showing multiple solid masses with unclear boundaries, irregular shapes, and nonuniform internal echoes.
Abdominal-pelvic computed tomography (CT) revealed multiple low-density masses in the abdominal cavity. The dimensions of the largest mass in the left abdominal cavity were approximately 14.7 cm × 13.2 cm, and the mass had a clear boundary and convoluted vascular course. After performing contrast-enhanced scans, the mass did not exhibit significant enhancement with a -65 HU value. Another mixed-density mass was observed in the right abdominal cavity, with dimensions of approximately 15.4 cm × 10.6 cm; following contrast-enhanced scans, its CT values during the three phases were approximately 28/31/50 HU (Figure 2).
Figure 2 Abdominal-pelvic computed tomography showing two masses.
The left one exhibited a fat-like density with a -65 HU value, a clear boundary, and a convoluted vascular course, and contrast-enhanced scanning did not show significant enhancement; the right one had a mixed density, and contrast-enhanced scanning yielded the following computed tomography values during the three phases: 28/31/50 HU.
Liposarcoma originates from primitive mesenchymal cells and usually occurs in the retroperitoneum, with approximately 35% of cases arising from perinephric fat. PRPLS accounts for approximately 45% of soft tissue sarcoma cases[2,3] with a prevalence of 0.3-0.4 cases per 100000 inhabitants. According to the morphological characteristics and cytogenetic variation, PRPLS is categorized by the World Health Organization into five subtypes: Well-differentiated; dedifferentiated; myxoid; pleomorphic; and mixed-type. The first two types are the most common in PRPLS, while the rarer subtypes (i.e., myxoid and pleomorphic) occur less often in the retroperitoneum.
Owing to the special position of PRPLS, the patients do not have obvious clinical manifestations in the early stages of the disease. Moreover, the tumors are often detected only after they are palpable in the abdomen. Since PRPLS has no characteristic symptoms, the complaints of patients commonly relate to discomfort, bellyache, bloating, and direct invasion or compression of other adjacent organs (e.g., the stomach, intestines, kidney, bladder, or great vessels). In this case, the patient presented with a complaint of abdominal bloating.
There are no significant laboratory abnormalities observed in the early stages. The preferred diagnostic method for PRPLS is examination through CT, which is also the essential reference standard in tumor staging and preoperative evaluation[7,15]. The typical CT imaging of PRPLS includes legibility of low-density tissue as fat component with large size and non-enhancement during the arterial phase. In a small number of cases, the kidney is usually displaced by mass compression or surrounded by the mass. This report shows two different patterns of appearance of PRPLS on CT, which have the same pathological type: Atypical lipomatous tumor/well-differentiated liposarcoma. One was observed in the left abdominal cavity, and demonstrated a fat-like density with a -65 HU value, a clear boundary, and a convoluted vascular course. Moreover, it had no significant enhancement after contrast-enhanced scanning. The other larger mass was a mixed-density mass observed in the right abdominal cavity, after contrast-enhanced scanning; its CT values during the three phases were approximately 28/31/50 HU.
In some cases, PRPLS was detected accidentally during a regular health checkup by ultrasound and color Doppler, which are preferred imaging methods to distinguish vascular lesions and soft tissue sarcoma because they can provide detailed information about vascular anatomy[16,17]. Recently, with the development of contrast-enhanced ultrasound technique that can effectively diagnose abdominal parenchymal diseases and vascular lesions in real time and without the use of ionizing radiation[18-21], it may provide a new perspective and possibility for researchers on the diagnosis of PRPLS.
At present, surgical treatment remains one of the primary modes of therapy for PRPLS. However, for patients who underwent macroscopically complete resection of PRPLS, a high recurrence rate remains following operation. PRPLS grows in a special location; hence, the tumor often has a large volume at the time of diagnosis. Enlargement of the tumor in the retroperitoneal space may drastically change the normal anatomy of the surrounding organs and great vessels through compression. This effect poses difficulties to surgons regarding the protection of the important organs and great vessels during surgery[22,23].
PRPLS is rarely confirmed with metastasis through the lymph gland. Thus, it is not essential to perform regional lymphadenectomy. The recurrence rate can be reduced by completely removing the tumor and the surrounding suspicious adipose tissue. In patients in whom the tumor has invaded adjacent organs or cannot be easily separated from great vessels, combined devisceration is an effective approach to reducing the risk of intraoperative hemorrhage and increasing the possibility of intact excision.
Postoperative recurrence of PRPLS, especially local recurrence, is relatively common. Previous studies have shown that the 5-, 8-, and 10-year crude cumulative incidences of local recurrence were 25.9%, 31.3%, and 35%. Different treatment policies influence the local recurrence outcomes of well-differentiated and dedifferentiated PRPLS without impacting overall survival, whereas deaths are related to locoregional recurrences. Resection of recurrent tumors is associated with prolonged patient survival.
Given that the possibility of cure after recurrence is low, a relatively conservative approach is taken for the resection of recurrent PRPLS after an extended primary procedure. The goal is to excise the recurrent tumor directly invading organs, rather than performing a wider excision, as performed for PRPLS.