title: Two malignant solitary fibrous tumors in one kidney: Case report and review of the literature.
abstract: Malignant solitary fibrous tumors of the kidney are very rare. Two tumors in one kidney is particularly rare and has not been previously reported. Due to the non-specific clinical symptoms, it is difficult but also very significant to give a definite diagnosis. Here, we report a case of two renal masses in one kidney. A 56-year-old man was admitted to our hospital complaining of shortness of breath, weakness, hyperhidrosis and intermittent hypoglycemia of 1-year duration without gross hematuria or lumbago. Imaging studies revealed two masses manifesting as inhomogeneous, with soft-tissue density and having no clear boundaries with the kidney. The patient was initially diagnosed with space-occupying lesions of the left kidney (with suspicions of renal cell carcinoma) and left radical nephrectomy was performed. Histologically, the tumors consisted of ovoid or spindle cells, and a hemangiopericytoma-like pattern and cellular atypia was observed in certain areas. Mitotic figures were more than 4 per 10 high-power fields. Immunohistochemically the tumor cells were positive for CD34, CD99 and vimentin. Accordingly, a diagnosis of malignant solitary fibrous tumor of the left kidney (low-grade malignance) was established. Postoperative follow-up of 10 months did not find tumor recurrence or metastasis and hypoglycemia was resolved with the removal of the tumors.
authors.affiliation: Department of Urology, Second Hospital of Tianjin Medical University, Tianjin Institute of Urology, Tianjin 300211,  P.R. China.
authors.forename: Guangning
authors.initials: G
authors.lastname: Zhao
authors.forename: Gang
authors.initials: G
authors.lastname: Li
authors.forename: Ruifa
authors.initials: R
authors.lastname: Han