Solitary Fibrous Tumor of the Kidney: A Case Report and Review of the Literature

Case Review

RIU0319_03-09.qxd 3/9/07 18:42 Page 36 CASE REVIEW Solitary Fibrous Tumor of the Kidney: A Case Report and Review of the Literature Kaoutar Znati, MD,* Laila Chbani, MD,* Hinde El Fatemi, MD,* Taoufik Harmouch, MD,* Imane Kamaoui, MD,† Fadl Tazi, MD,‡ Sanae Bennis, MD,* Afaf Amarti, PhD* Departments of *Pathology, †Radiology, and ‡Urology, Al Ghassani Hospital, University Hospital Hassan II, Fez, Morocco A solitary fibrous tumor (SFT) is an unusual spindle cell neoplasm that usually occurs in the pleura but has recently been described in diverse extrapleural sites. Urogenital localization is rare, and only 19 cases of SFT of the kidney have been described. We report a case of a large SFT clinically thought to be renal cell carcinoma arising in the kidney of a 70-year-old man. The tumor was well circumscribed and composed of a mixture of spindle cells and dense collagenous bands, with areas of necrosis or cystic changes noted macroscopically and microscopically. Immunohistochemical studies revealed reactivity for CD34, CD99, and Bcl-2 protein, with no staining for keratin, S-100 protein, or muscle markers, confirming the diagnosis of SFT. This tumor is benign in up to 90% of cases. The immunohistochemical study is the key to diagnosis. [Rev Urol. 2007;9(1):36-40] © 2007 MedReviews, LLC Key words: Immunohistochemical study • Kidney • Renal neoplasm • Solitary fibrous tumor • Spindle cells solitary fibrous tumor (SFT) is an unusual spindle cell neoplasm of adults that was first described in 1931.1 This type of tumor usually occurs in the pleura but has recently been described in diverse extrapleural sites. Urogenital localization is rare. To our knowledge, only 19 cases of SFT of the kidney have been reported (Table 1), and the origin of these tumors remains controversial.2-16 In general, they are slow-growing tumors with a favorable prognosis, although there have been some malignant cases. This case study describes an SFT A 36 VOL. 9 NO. 1 2007 REVIEWS IN UROLOGY RIU0319_02-13.qxd 2/14/07 6:08 PM Page 37 Solitary Fibrous Tumor of the Kidney Table 1 Clinicopathologic Findings of 19 Renal Solitary Fibrous Tumors Case No. Year Authors Age of Patient (y) Sex of Patient Site Size (cm) Treatment Follow-up 1 1996 Gelb AB et al 45 M R kidney 3
2.5
1.5 Rad Np Died (3 mo) 2 1996 Fain JS et al3 45 M R kidney 6
5
3.5 Rad Np 8 mo; NED 3 1996 Fain JS et al3 46 F R kidney 7.2
6
5.5 Rad Np 33 mo; NED 4 1996 Fain JS et al3 51 M L kidney 4.5
4
2.5 Rad Np 2 mo; NED 5 1997 Fukunaga M and Nikaido T4 33 F R renal peripelvis 3
2.5
2.5 R Np 2 mo; NED 6 1997 Fukunaga M and Nikaido T4 36 F L renal peripelvis 2
1.5
1.5 L Np 12 mo; NED 7 1999 Hasegawa T et al5 64 M R kidney 4.5 Rad Np 8 mo; NED M R renal pelvis 6
4.5
4 Rad Np 60 mo; NED 2 6 8 2001 Yazaki T et al 70 9 2000 Morimitsu Y et al7 72 F L kidney 8 Rad Np 10 mo; NED 10 2001 Wang J et al8 41 M L kidney 14
12
7 L Np 4 y; NED 11 2001 Wang J et al8 72 M R kidney 13
9
7 R Np 5 mo; NED 12 2002 Magro G et al9 31 F R kidney 8.6 Rad Np 8 mo; NED 13 2003 Llarena Ibarguren R et al10 51 F Bilateral 25 (L) 2 (R) Resection NED 14 2004 Kunieda K et al11 53 M R kidney 14
13
10 R Np NED 15 2004 Yamada H et al 59 M Renal capsule 6.8
4.4 L Np 4 y; NED 16 2005 Yamaguchi T et al13 51 F L kidney 10
5
10 L Np NED 17 2005 Johnson TR et al14 51 F R kidney 11 Rad Np NED 18 2006 Alvarez Mugica M et al15 36 M R kidney Rad Np NED 19 2006 Fine SW et al16 76 M L kidney 12 Rad Np Malignant Our case 2006 Znati K et al 70 M L kidney 15
12
4 Rad Np 6 mo; NED 12 NED, no evidence of disease; Np, nephrectomy; Rad, radical; R, right. arising in the kidney, the final diagnosis of which was made by immunohistochemical study. We discuss the clinicopathologic features of SFTs, the differential diagnosis, and prognosis of renal spindle cell neoplasms. Case Report A 70-year-old man complained of pain in his left lower back and hematuria of 1-month duration. The clini- cal examination revealed a left renal tumor. Laboratory data revealed no abnormalities. Computed tomography demonstrated a well-delineated, encapsulated tumor of the left kidney that exhibited enhancement with contrast medium and measured approximately 15 cm in diameter (Figure 1). The tumor involved the renal cortex and extended extensively into the perirenal adipose tissue. A mag- netic resonance imaging (MRI) scan showed the tumor to be of low intensity on T1-weighted images and of irregular high intensity on T2-weighted images. No renal vein or inferior vena cava thrombosis was seen. No enlarged lymph nodes were seen in the abdomen. The patient underwent radical nephrectomy without complications. He is alive and has no evidence of disease 6 months after the surgery. VOL. 9 NO. 1 2007 REVIEWS IN UROLOGY 37 RIU0319_02-13.qxd 2/14/07 6:08 PM Page 38 Solitary Fibrous Tumor of the Kidney continued Figure 1. Contrast computed tomography scan demonstrating an enhanced, well-demarcated tumor of the left kidney with multinodular configuration. The tumor involved the renal cortex and perirenal adipose tissue. Pathologic Findings Discussion The cut section of the resected left kidney revealed a vaguely multinodular, grayish to white, firm, heterogenous tumor with cystic and necrotic changes. The tumor occupied the entire kidney and had slightly invaded the cortex and perirenal adipose tissue. Microscopically, the mass consisted of bland, spindle-shaped cells with scant cytoplasm accompanied by prominent hyalinized collagenous tissue that was patternless or showed hemangiopericytomatous patterns (Figure 2). The cells lacked cytologic atypia and showed no mitosis. The tumor focally infiltrated the renal cortex, and some of the glomeruli and renal tubules were entrapped. The tumor was continuous to the renal capsule; however, the precise relationship between them was ambiguous. An immunohistochemical study was carried out with formalin-fixed, paraffin-embedded sections. The tumor cells were diffusely positive for CD34 (Figure 3), CD99, and Bcl-2. However, staining for cytokeratin, -smooth muscle actin (-SMA), S-100 protein, and p53 was negative for the tumor cells. The Ki67 index was also negative. Based on the histologic and immunohistochemical features, a diagnosis of SFT was established. The SFT is a rare but well-established neoplasm. Indeed, in 1942, Stout and Murray17 introduced the concept that hemangiopericytoma originated from 38 VOL. 9 NO. 1 2007 Figure 2. Microscopic features of the solitary fibrous tumor. The tumor showed a hemangiopericytomatous growth pattern. Figure 3. The tumor cells stained diffusely and strongly for CD34. The vascular endothelium was also positive. REVIEWS IN UROLOGY the pericytes of blood vessels. In 1994, Fletcher18 proposed that hemangiopericytomas are heterogeneous in nature and may consist of SFTs and other distinctive soft tissue tumors, although the concept of hemangiopericytoma had been widely accepted. The new edition of the World Health Organization classification describes “hemangiopericytoma” as consisting of SFT and related conditions, including giant cell angiofibroma and lipomatous hemangiopericytoma. Solitary fibrous tumors arise most frequently in the pleura; however, occurrences of these tumors at sites other than the pleura have been described in recent years. Extrapleural tumors have occurred in the upper respiratory tract, lung, nasal cavity, paranasal sinuses, orbits, mediastinum, RIU0319_02-13.qxd 2/14/07 6:08 PM Page 39 Solitary Fibrous Tumor of the Kidney major salivary glands, breast, meninges, liver, and urogenital organs. Of the renal SFTs reported in the literature during the past 10 years, more than 50% have occurred in patients older than 40 years (from 33 to 76 years, with an average age of 52 years). The male-to-female ratio appears to be almost equal (1:1.5). 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.2,9,12 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. lular areas separated from each other by thick bands of hyalinized, somewhat keloidal collagen and branching hemangiopericytoma-like vessels.2-16 Electron microscopy reveals fibroblast-like tumor cells with rough endoplasmic reticulum and scattered mitochondria embedded in a collagenous matrix. Therefore, because of the Although most cases are benign, the behavior of SFTs is unpredictable. Roughly 10% to 15% of these tumors behave aggressively; thus long-term follow-up is mandatory. absence of characteristic findings on electron microscopy, it is not necessarily an indispensable technique. Instead, the immunohistochemical study is the key to diagnosis. CD34 im- Interestingly, one SFT of the kidney showed an intrarenal growth pattern without connection to the renal capsule or renal pelvis. Interestingly, one SFT of the kidney showed an intrarenal growth pattern without connection to the renal capsule or renal pelvis.8 Further research is necessary to clarify the pathogenesis of these rare tumors. 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.2-16 Except for those in case 19 and our case, no tumor contained areas of cystic change, hemorrhage, or foci of necrosis.16 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 hypercel- hemangiopericytomatous patterns. Diffuse positive expression of CD34, Bcl-2, and CD99 and negative expression of cytokeratin, -SMA, S-100, CD31, and c-kit are useful for their differential diagnosis.9,19 Although most cases are benign, the behavior of SFTs is unpredictable. Roughly 10% to 15% of these tumors munoreactivity 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. Seventy percent of SFTs express CD99 and Bcl-2; only 20% to 35% are variably positive for epithelial membrane antigen and smooth muscle actin. Focal and limited reactivity of S-100 protein, cytokeratins, and/or desmin has also occasionally been reported.8,19 Mesenchymal tumors that should be differentiated from SFT include sarcomatoid renal cell carcinoma, angiomyolipoma, fibroma, fibrosarcoma, leiomyoma, leiomyosarcoma, schwannoma, malignant peripheral nerve sheath tumor, hemangioma, angiosarcoma, synovial sarcoma, and gastrointestinal stromal tumor because these tumors typically show behave aggressively; thus longterm follow-up is mandatory. The histopathologic features related to clinical malignancy include increased cellularity, pleomorphism, increased mitotic activity ( 4 mitoses/10 highpower fields), necrosis, hemorrhage, and atypical location (parietal pleura, pulmonary parenchyma). However, there is far less information regarding the behavior of extrathoracic SFTs.19 To summarize, we report a case of an SFT arising in the kidney with characteristic histology of spindleshaped cells distributed in a haphazard pattern. The tumor cells are CD34 and Bcl-2 positive and -SMA and S-100 protein negative, consistent with the immunohistochemical profile for SFTs. Although SFTs in extrapleural sites remain uncommon, they should be considered in the differential diagnosis of spindle cell neoplasms. References 1. 2. 3. 4. Klemperer P, Rabin CB. Primary neoplasm of the pleura: a report of five cases. Arch Pathol. 1931;11:385-412. Gelb AB, Simmons ML, Weidner N. Solitary fibrous tumor involving the renal capsule. Am J Surg Pathol. 1996;20:1288-1295. Fain JS, Eble J, Nascimento AG, et al. Solitary fibrous tumor of the kidney: report of three cases. J Urol Pathol. 1996;4:227-238. Fukunaga M, Nikaido T. Solitary fibrous tumour of the renal peripelvis. Histopathology. 1997;30: 451-456. VOL. 9 NO. 1 2007 REVIEWS IN UROLOGY 39 RIU0319_02-13.qxd 2/14/07 6:08 PM Page 40 Solitary Fibrous Tumor of the Kidney continued 5. Hasegawa T, Matsuno Y, Shimoda T, et al. Extrathoracic solitary fibrous tumors: their histological variability and potentially aggressive behavior. Hum Pathol. 1999;30:1464-1473. Yazaki T, Satoh S, Iizumi T, et al. Solitary fibrous tumor of renal pelvis. Int J Urol. 2001;8:504508. Morimitsu Y, Nakajima M, Hisaoka M, Hashimoto H. Extrapleural solitary fibrous tumor: clinicopathologic study of 17 cases and molecular analysis of the p53 pathway. APMIS. 2000;108:617-625. Wang J, Arber DA, Frankel K, et al. Large solitary fibrous tumor of the kidney: report of two cases and review of the literature. Am J Surg Pathol. 2001;25:1194-1199. Magro G, Cavallaro V, Torrisi A, et al. Intrarenal solitary fibrous tumor of the kidney report of a case with emphasis on the differential diagnosis in the wide spectrum of monomorphous spindle 6. 7. 8. 9. 10. 11. 12. 13. 14. cell tumors of the kidney. Pathol Res Pract. 2002;198:37-43. Llarena Ibarguren R, Eizaguirre Zarzai B, Lecumberri Castanos D, et al. Bilateral renal solitary fibrous tumor. Arch Esp Urol. 2003;56:835-840. Kunieda K, Tanaka Y, Nagao N, et al. Large solitary fibrous tumor of the retroperitoneum: report of a case. Surg Today. 2004;34:90-93. Yamada H, Tsuzuki T, Yokoi K, Kobayashi H. Solitary fibrous tumor of the kidney originating from the renal capsule and fed by the renal capsular artery. Pathol Int. 2004;54:914-917. Yamaguchi T, Takimoto T, Yamashita T, et al. Fat-containing variant of solitary fibrous tumor (lipomatous hemangiopericytoma) arising on surface of kidney. Urology. 2005;65:175. Johnson TR, Pedrosa I, Goldsmith J, et al. Magnetic resonance imaging findings in solitary fibrous tumor of the kidney. J Comput Assist Tomogr. 2005;29:481-483. 15. 16. 17. 18. 19. Alvarez Mugica M, Jalon Monzon A, Fernandez Gomez JM, et al. Solitary pararenal fibrous tumor. Arch Esp Urol. 2006;59:195-198. Fine SW, McCarthy DM, Chan TY, et al. Malignant solitary fibrous tumor of the kidney: report of a case and comprehensive review of the literature. Arch Pathol Lab Med. 2006;130:857-861. Stout AP, Murray MR. Hemangiopericytoma: a vascular tumor featuring Zimmerman’s pericytes. Ann Surg. 1942;116:26-33. Fletcher CDM. Haemangiopericytoma. A dying breed? Reappraisal of an entity and its variants: a hypothesis. Curr Diag Pathol. 1994;1:19-23. Guillou L, Fletcher JA, Fletcher CDM, et al. Extrapleural solitary fibrous tumour and haemangiopericytoma: World Health Organization classification of tumours. In: Fletcher CDM, Unni KK, Mertens F, eds. Pathology and Genetics of Tumours of Soft Tissue and Bone. Lyon, France: IARC Press; 2002:86-90. Main Points • Solitary fibrous tumors (SFTs) are unusual spindle cell neoplasms of adults that typically occur in the pleura but have been described in diverse extrapleural sites. Urogenital localization is rare; to the authors’ knowledge, only 19 cases of SFT of the kidney have been reported. • The origin of SFTs remains controversial, and further research is necessary to clarify the pathogenesis of these tumors. • 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 hemangiopericytomalike vessels. • Immunohistochemical study is the key to diagnosing SFTs. CD34 immunoreactivity has been shown to be strongly and diffusely expressed in many of these tumors, 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. • Although most SFTs are benign, their behavior is unpredictable. Roughly 10% to 15% of these tumors behave aggressively; thus long-term follow-up is mandatory. 40 VOL. 9 NO. 1 2007 REVIEWS IN UROLOGY