Giant Retroperitoneal Liposarcoma Mimicking Ovarian tumour - A Case report

Abstract

Retroperitoneal liposarcomas are rare tumours representing less than 1% of all malignant tumours. They are generally slow growing and may attain enormous sizes.

We report a case of a giant (9.8kg) retroperitoneal liposarcoma in a 65 years old lady which was initially misdiagnosed as an ovarian tumour. She had a successful surgical removal and has been followed up for more than one year with no evidence of recurrence.

Introduction

Liposarcomas are neoplasms of mesordermic origin derived from adipose tissues; they make up 10-14% of all soft tissue sarcomas but represent less than 1% of all malignant tumours1. They could occur anywhere in the body where adipose tissues are in abundance especially in the extremities with a predilection for the thigh. Between 12-40% occur in the retroperitoneum2. Retroperitoneal liposarcomas alone comprises 0.1-0.2% of all neoplasias2,3. It can originate from any part of the retroperitoneum and hence pose a great challenge in the diagnosis of abdominal masses. They are generally slow growing and may attain enormous sizes.

We report the case of an elderly patient with a giant (9.8kg) retroperitoneal liposarcoma that was initially misdiagnosed as an ovarian tumour.

Reports

A 65 years old p3+0 woman presented to our surgical service with 3 years history of vague abdominal pain and a slowly progressing abdominal swelling which started from the lower part of the abdomen. She was 15 years post menopausal and had no history of bleeding per vaginam. Her first delivery was at 17 years of age and her last child birth was 18 years ago. There were no gastrointestinal, genitourinary or cardiopulmonary symptoms. She was not diabetic nor hypertensive.

She was not in any form of distress, not pale, anicteric and well hydrated with no peripheral oedema. Her pulse rate was 92bpm, BP was 170/90mmHg and her chest was clinically clear. Her abdomen was grossly distended with an irregular mass originating from the pelvis and extending to the epigastrium, though nontender and with no ascites. Liver and spleen were not palpable. Pelvic and digital rectal examinations did not reveal any abnormality.

Abdominopelvic ultrasound scan was reported as right sided thick walled hypo-echoic adnexal mass measuring 17.5×6.7cm in size. There was echogenic collection within the peritoneal cavity associated with thickening of the bowel loops. Other organs were normal and no intra abdominal lymphadenopathy. The tumor, on ultrasonography, was consistent with a right ovarian tumour with pseudomyxoma peritonei.

Her haemoglobin, urea, electrolytes, creatinine, liver function test, chest x-ray and ECG were all normal. She could not afford a CT scan.

She was counseled and prepared for exploratory laparotomy. The operative findings were a huge encapsulated retroperitoneal mass occupying the entire pelvis extending to the epigastrium and displacing the intestines upward (fig. 1). The ureters were displaced laterally. The ovaries, uterus, liver and spleen appeared normal. There was no ascites or lymphadenopathy. The mass was completely excised and weighed 9.8kg (fig 2). She did well and was discharged after a week and had remained symptom-free after one year follow-up. The histology of the resected mass was consistent with a well differentiated liposarcoma (fig. 3).

Conclusions

In conclusion, although retroperitoneal tumours are not common, they should always be considered in evaluating patients with abdominal and pelvic masses. CT scan should be employed for diagnosis when ultrasonography is unreliable.

Discussion

Primary retroperitoneal tumours are rare and they have great histological variety having originated from retroperitoneal adipose, muscle, connective tissue, lymphatics and nerve fibres and also from the urogenital tract.

About 85% of retroperitoneal tumours are malignant and of these liposarcoma is the most common histopathological type, though they represent less than 1% of all neoplasms1,2,3. Liposarcomas occur at any age, but the majority occur in the age 40-60 years with a peak incidence at the fifth decade of life3. Generally it has a male predominance but with no racial preponderance2,5.

They are generally slow growing tumours and may attain enormous sizes especially when they occur in a clinically silent retroperitoneum, hence may attain giant sizes3. Inoue et al reported the case of an eighteen kilogram retroperitoneal liposarcoma 4.

Patients with retroperitoneal liposarcomas usually present late, this is because these tumours arise in the large potential space of the retroperitoneum and can grow very large without producing symptoms. Usually there are no subjective symptoms, moreover when symptoms do occur, they are non specific and include abdominal discomfort, pain and fullness and can easily be mistaken for other gastrointestinal or gynaecological conditions5,7. Symptoms when they occur, are usually due to pressure on other abdominal or pelvic viscera.

The diagnosis of retroperitoneal tumours can be difficult, this is especially so in the developing world where CT and MRI are not readily available and affordable. The index patient could not afford CT scan. Since there are no specific symptoms, we relied on ultra sonograhy which is cheaper and affordable but misdiagnosed the lesion as an ovarian tumour. This underpins the subjectivity of ultrasonography as it is operator-dependent. This index case re-emphasizes the need for the National Health Insurance programme to be all inclusive in order for the poor in our society to benefit; this would have covered this patient for CT scan and thus correct diagnosis before surgery.

It is generally agreed that aggressive radical excision is the treatment of choice of all liposarcomas whenever they occur1,6,7. The line of dissection must be well beyond the palpable or visible limits of the tumour and its pseudocapsule. Recurrence is invariable after incomplete excision or enucleation of a pseudo-encapsulated liposarcoma. Although this patient was not planned for excision of liposarcoma because of the misdiagnosis, efforts were made to excise the entire macroscopic tumour and confirmation by tumor-free line of resection.

The use of radiotheraphy is still controversial8,9. The slow growing, well-differentiated liposarcomas are relatively radioresistant. Radiotherapy is generally employed in the treatment of incompletely resected tumours, recurrence at primary site, inoperable primary tumours and metastatic disease. They are also non responsive to various combinations of chemotheraphy6,8,9,10. Our patient was neither given adjuvant chemotheraphy nor radiotheraphy, yet she is clinically disease -free at one year post surgery as confirmed by CT scan one year post-operatively.

Figure 1:

Intra-operative finding of huge, mobile retroperitoneal mass

Figure 2:

The resected tumour

Figure 3:

Histology of the resected mass shows a well differentiated liposarcoma