[Malignant fibrous histiocytoma originating in a renal capsule: a case report]

We report a case of malignant fibrous histiocytoma originating in a renal capsule. A 43-year-old woman was admitted with a chief complaint of right lower abdominal pain. Physical examination was unremarkable. Serum C-reactive protein and erythrocyte sedimentation rate increased to 3.8 mg/dl and 60 mm/hr., respectively. Computed tomography (CT) and magnetic resonance image (MRI) showed a heterogeneous enhanced mass, 4 x 9 x 13 cm in size, in contact with the lateral part of the right kidney. Selective right renal arteriography revealed a hypovascular tumor, the main feeding artery of which was the right adrenal artery. Preoperative clinical diagnosis was a retroperitoneal sarcoma and transabdominal tumor resection was performed. The adhesion between the tumor and the right kidney was so severe that right nephrectomy was also necessary for a radical surgery. The tumor, measuring 13 x 9 x 6 cm, was located laterally adhering to the right renal capsule. Microscopic examination of the tumor demonstrated spindle-shaped fibroblast-like cells arranged in a storiform pattern with fibrous stroma and clusters of rounded histiocyte-like cells and pleomorphic giant cells with bizarre nuclei. Histopathological diagnosis was malignant fibrous histiocytoma arising from the renal capsule and there was no tumor invasion to renal parenchyma. No adjuvant therapy was performed but she has remained well for 31 months since the operation without evidence of disease.