Solitary fibrous tumor of kidney: A case report
Li-Ren Fang, Sheng-Han Tsai, Luke S. Chang, Hsiao-Hsian Wang, Kuang-Kuo Chen,Chieh-Chen Hsieh, Chia-Lun Wang, Chin-Wei Yang,
Department of Urology, Cheng Hsin General Hospital
Introduction: Solitary fibrous tumors (SFT) are rare growths of soft tissue cells that can form nearly anywhere in the body. Solitary fibrous tumors most often occur in the lining around the outside of the lungs (pleural solitary fibrous tumors). Most solitary fibrous tumors are benign, but in rare cases, solitary fibrous tumors can be malignant. Solitary fibrous tumors tend to grow slowly and may not cause signs and symptoms until they become very large.Approximately 78% to 88% of SFT's are benign and 12% to 22% are malignant.
Case report: This is a 72 years old female with documented Type 2 diabetes mellitus, cervical cancer status post abdominal total hysterectomy and bilateral salpingo-oophorectomy and hyperlipidemia. She was told to have left renal mass during follow-up CT of abdomen: a relatively low density nodule measuring about 4.6x4.2x6.8 cm in size in the medial portion of the lower pole of left kidney was seen. Due to the lack of contrast enhancement on the inital CT, a further contrast MRI of abdomen was done: a well defined soft tissue mass about 5.81x4.00x7.18cm, with low T1WI, high T2WI signal, with vivid contrast enhancement on the arterial phase, with no wash-out seen either on the portal or delayed phase, on the medial aspect of the low pole of the left kidney was seen. No lymph node involvement or distant metastasis was seen. After explaining to the patient the possible differential diagnosis, as well as malignant potential, the patient consented for surgical resection of the renal tumor. She was subsequently admitted for Da Vinci assisted partial nephrectomy. Pathology report proved solitary fibrous tumor with positivity for for CD34 and STAT6
Discussion: The origin of most cases of SFT of the kidney is difficult to determine. Some reported cases of solitary fibrous tumor of the kidney were reported to have originated from the renal capsule. In our case study, the tumor exhibited a unique growth pattern as a primary tumor of the kidney. The tumor involved not only the renal cortex but also the extrarenal soft tissue, suggesting the possibility of a renal surface origin of the tumor. Interestingly, one SFT of the kidney showed an intrarenal growth pattern without connection to the renal capsule or renal pelvis.Grossly, the renal SFTs reported in the literature ranged from 2 to 25 cm (mean, 8.75 cm). Most of the lesions were described as well-circumscribed or pseudoencapsulated, lobulated, rubbery or firm masses with a homogeneous, gray or tan-white, whorled cut surface.Except for those in case 19 and our case, no tumor contained areas of cystic change, hemorrhage, or foci of necrosis.In all the reported cases of SFT of the kidney, final diagnosis was made by means of pathology. All tumors were characterized by spindle cell proliferation showing a patternless architecture with a combination of alternating hypocellular and hypercellular areas separated from each other by thick bands of hyalinized, somewhat keloidal collagen and branching hemangiopericytoma-like vessels.CD34 immunoreactivity has been reportedly shown to be strongly and diffusely expressed in many cases of SFT, and although it is not specific for SFT, strong CD34 reactivity is currently regarded as characteristic and an indispensable finding in the diagnosis of SFT