Introduction: Soft tissue sarcomas represent less than 1.5% of malignant tumors. They are characterized by destructive growth, recurrence, and distant metastases to the lungs. The sites more frequently affected are the extremities in 40% and the retroperitoneum in 15–20% of the cases. Case description: A 57-year-old female presented reporting a history of pain for 12 months and a progressively growing abdominal mass. The initial histological analysis indicated a diagnosis of lipoma in the mesentery, but a nuclear magnetic resonance of the abdomen showed two retroperitoneal masses. After laparoscopic resection, immunohistochemistry confirmed a well-differentiated liposarcoma and myxoid liposarcoma. One year later, the patient had a second surgical intervention due to tumor relapse, with pathology showing a well-differentiated liposarcoma. Discussion: Mixed-type liposarcoma is the most uncommon histotype. It is still an unknown entity. It shows the combined features of myxoid/round and liposarcoma well-differentiated/dedifferentiated. Also, it can show the characteristics of the myxoid subtype/round or pleomorphic liposarcoma. All these different presentations generate conceptual conflicts when establishing the protocols for management and treatment. Conclusion: Mixed-type liposarcoma represents the most uncommon subtype of liposarcoma. Complete surgical resection with negative margins remains the standard of treatment. In order to achieve negative margins, en bloc multivisceral resection and neoadjuvant therapies (chemotherapy or radiotherapy) are often necessary in selected cases.