RÉSUMÉ
@#Retroperitoneal liposarcoma is an uncommon tumor both in the pregnant and nonpregnant state. Its exact incidence is unknown because of its rarity. Due to its propensity for local recurrence, prognosis depends on histologic subtype and negative margins of resection. Surgery remains the mainstay of treatment, and timing is critical in terms of finding a surgically resectable lesion while balancing fetal risks. This report describes tumor recurrence in a pregnancy with a prior history of surgery for an atypical lipomatous tumor presenting as a retroperitoneal mass. After discussion with the multidisciplinary team, as well as with the patient’s consent, the plan was to defer surgery until 34 weeks, followed by scheduled tumor removal 2 weeks postpartum. She delivered abdominally to a baby girl with a good outcome. Histopathology showed dedifferentiated liposarcoma with a positive tumor margin. The patient has survived at 6-month follow-up and completed four cycles of chemotherapy with doxorubicin, ifosfamide, and mesna. However, surveillance imaging again showed tumor recurrence.