Asymptomatic giant retroperitoneal mass detected at a medical checkup.

The differential diagnosis of retroperitoneal mass includes liposarcoma, leiomyosarcoma, malignant fibrous histiocytoma, neurofibroma, stromal tumor, teratoma, and lymphoma. Leiomyosarcoma is rare with poorer prognosis than other soft tissue sarcomas. Soft tissue sarcoma of retroperitoneal origin often remains asymptomatic until tumor enlargement, leading to diagnosis at advanced stages.