De novo malignant solitary fibrous tumor of the kidney

Abstract

The kidney is a relatively infrequent site for solitary fibrous tumor (SFT). Among the previously reported cases, only two cases of malignant renal SFT developing via dedifferentiation from a pre-existing benign SFT have been reported. Here we reported a case of de novo malignant renal SFT clinically diagnosed as renal cell carcinoma in a 50-year-old woman. The tumor was circumscribed but unencapsulated and showed obvious hemorrhagic necrosis. Microscopically, the tumor was composed of patternless sheets of alternating hypercellular and hypocellular areas of spindle cells displaying mild to moderate nuclear atypia, frequent mitoses up to 8 per 10 high power fields, and a 20% Ki-67 proliferative index. Immunohistochemical studies revealed reactivity for CD34, CD99 and vimentin, with no staining for all other markers, confirming the diagnosis of SFT. No areas of dedifferentiation were seen after extensive sampling. Based on the pathologic and immunohistochemical features, a diagnosis of de novo malignant renal SFT was warranted. Our report expands the spectrum of malignant progression in renal SFTs. Even though this patient has been disease-free for 30 months, long-term follow-up is still mandatory.

Solitary Fibrous Tumors of the Kidneys: Presentation, Evaluation, and Treatment

“…Again, however, these symptoms are rare, and renal SFTs are found mostly on an incidental basis during radiologic studies, as shown by Hsieh et al [8]. However, renal SFTs, as opposed to renal cell carcinomas, cause almost no paraneoplastic syndromes.…”

“…The vast majority of renal SFTs exhibit benign behavior, with only 5 malignant cases reported in the literature with secondary metastasis, such as to the thoracic vertebral spine [8,20]. Although the clinical course of SFTs is rather unpredictable, the prognosis of SFTs is generally favorable.…”

“…Clinical presentation varies between an incidental finding of a mass on radiological imaging to a palpable mass [8]. Flank pain or abdominal pain, along with gross hematuria, are among the common symptoms.…”

“…Therefore, an SFT is considered an ‘intermediate malignant, rarely metastasizing' neoplasm [21]. A malignant SFT is postulated to develop via two pathways: (1) de novo occurrence or (2) dedifferentiation or sarcomatous overgrowth from a preexisting histologically benign SFT [8]. …”

Ürogenital Sistem Yerleşimli Soliter Fibröz Tümör: İki Olgu Sunumu

“…Biz, burada ekstraplevral nadir yerleşimli, böbrek ve mesanelokalizasyonlu2 SFT olgumuzu;ayırıcı tanı açısındanhis-topatolojik ve immünhistokimyasal özellikleri ile birlikte sunacağız. (6). Mesane lokalizasyonlu olgumuzda 10 BBA da mitoz izlenmezken, böbrek lokalizasyonlu olgumuzda ise 1 adet mitoz tespit edilmiştir.SFT' lerin çoğunluğu benign olmasına rağmen literatürdemalign olgular da bildirilmiştir (7).…”