Solitary Fibrous Tumor of the Kidney: A Case Report

Solitary fibrous tumor is a spindle cell neoplasm mostly originating from pleura; however, it has also recently been reported to be extrapleural. A 57-year-old man presented with left lumbal pain. Ultrasonography and computed tomography showed a cystic lesion of 14 × 11？cm with solid areas and septations in middle and lower poles of the left kidney. Radical nephrectomy was performed. Immunohistochemical studies showed strong reactions with CD34 and CD99. A nuclear positivity with Ki-67 was observed in less than 1% of cells. Despite repeated stainings with vimentin, no clear tumor evaluation could be made due to artifacts. The tumor was negative with Bcl-2, desmin, HMB-45, S100, FVIII, and CD31. Histopathological and molecular studies made the diagnosis of a solitary fibrous tumor. The patient is now currently free of disease at the 26th month of followup. 1. Introduction Although fibrous tumors mostly originate from pleura, tumors originating from urogenital system organs such as kidney, prostate, and urinary bladder have also been reported [1]. Solitary fibrous tumor (SFT) of the kidney is a rare mesenchymal cell tumor. SFT of the kidney was first defined by Gelb et al. in 1996 [2]. Nearly 50 cases of SFT of the kidney have been reported so far in the literature. Most of these types of tumors have a benign character [3]. It is difficult to differentiate it from renal cell carcinoma with imaging techniques. Definitive diagnosis can be made by pathological examinations including immunohistochemical and molecular techniques. In this paper, we present a case who was operated with radical nephrectomy and whose pathology result was reported as SFT. 2. Case Report A 57-year-old male patient presented with a left lumbal pain for 3 days. Physical examination with palpation revealed firm and mobile mass in upper left quadrant of the abdomen. No costovertebral tenderness was present. Urinalysis showed 3 erythrocytes. Laboratory data were as follows: blood urea nitrogen 16？mg/dL, creatinine 0.9？mg/dL, and hemoglobin 13.3？g/dL. Ultrasonography demonstrated a 14？cm vascularized, cystic, space-occupying formation with septations and solid components in middle and lower poles of the left kidney. Computed tomography identified a 14 × 11？cm cystic, space-occupying formation with many thick septae, which originated from anterior cortex of the left kidney and reached the level of pelvic inlet (Figure 1). Doppler ultrasonography showed patent main renal vessels and vena cava, none with thrombus within. Thoracic tomography showed a millimetric nodule in the left lower lobe