Objectives: To report one case of a large retroperitoneal malignant fibrohistiocytoma.
Methods/results: 40-year-old female with the diagnosis of a large right retroperitoneal mass after a study for right flank pain and weight loss over several months. Surgery was performed with excision of a large tumor; the pathologic diagnosis was malignant fibrohistiocytoma.
Conclusions: Primary retroperitoneal tumors are rare neoplasias, usually diagnosed in advanced stages. The malignant fibrohistiocytoma is an infrequent entity with difficult histological diagnosis and poor prognosis. To date, the only valid option is surgery, because adjuvant treatments do not offer clear advantages today.