A Rare Case of Deep Fibrous Histiocytoma with Low-Grade Myxoid and Dedifferentiated Liposarcoma Features: Clinical, Radiological, and Histopathological Insights

Background: Deep fibrous histiocytoma (DFH) is a rare benign mesenchymal tumor usually located in the dermis or subcutaneous tissue. Retroperitoneal presentation is exceedingly rare. We report a case of retroperitoneal DFH with liposarcomatous differentiation, emphasizing its clinical, radiological, and pathological features. Case Presentation: A 53-year-old male presented with postprandial dyspepsia and increased bowel movements. Imaging revealed a large retroperitoneal mass compressing major abdominal vessels. The patient underwent a xipho-pubic laparotomy with complete en bloc resection of a 12-kg mass. Histopathology demonstrated a spindle-cell neoplasm consistent with DFH showing low-grade myxoid and dedifferentiated liposarcomatous areas. Immunohistochemistry showed CD34 positivity and negativity for S100 and SMA. Conclusion Retroperitoneal DFH with liposarcomatous features represents a diagnostic challenge due to its rarity and overlapping features with soft tissue sarcomas. Complete surgical resection remains the treatment of choice, and close postoperative follow-up is warranted to monitor recurrence.