Case Reports in Urology

Case Reports in Urology / 2016 / Article

Case Report | Open Access

Volume 2016 |Article ID 2426874 |

Wataru Usuba, Hideo Sasaki, Hidekazu Yoshie, Kazuki Kitajima, Hiroya Kudo, Ryuto Nakazawa, Yuichi Sato, Masayuki Takagi, Tatsuya Chikaraishi, "Solitary Fibrous Tumor of the Kidney Developing Local Recurrence", Case Reports in Urology, vol. 2016, Article ID 2426874, 8 pages, 2016.

Solitary Fibrous Tumor of the Kidney Developing Local Recurrence

Academic Editor: Phillip M. Pierorazio
Received21 Jan 2016
Revised30 Mar 2016
Accepted07 Apr 2016
Published28 Apr 2016


Solitary fibrous tumor (SFT) of the kidney is a rare entity and usually displays a favorable prognosis. We herein report a second case of renal SFT developing local recurrence. A 50-year-old man was referred to our hospital because of a left renal mass. An abdominal CT detected a large renal tumor and radical nephrectomy was performed with a possible diagnosis of renal cell carcinoma. The resected tumor size was measured at 17 × 11 × 8 cm. Grossly, necrosis was observed in central lesion of the tumor but hemorrhage was not observed. Microscopically, the tumor consisted of spindle-shaped cells with scant cytoplasm accompanied by hyalinized collagenous tissue, which displayed hemangiopericytomatous patterns. The cellularity was normal and nuclear pleomorphism was not observed. Ki-67 labeling index was less than 3%. The pathological diagnosis of SFT was made without obvious malignant findings. Three years after the surgery, a follow-up CT scan detected a mass lesion in the tumor bed. Surgical resection was performed and the resected tumor was compatible with local recurrence of the SFT without obvious malignant findings. Renal SFT should be carefully monitored even in the absence of obvious malignant findings.

1. Introduction

Solitary fibrous tumor (SFT) is a clinical entity that was first reported as a tumor of the pleura in 1931 and usually arises in the pleura [1]. SFT is a rare spindle cell neoplasm and it is postulated that the tumor originated from mesenchymal tissue [2]. Histologically SFT shows hemangiopericytoma-like growth pattern and immunohistochemical staining for CD-34 and Bcl-2 is helpful for diagnosing the SFT. SFT typically is strong and diffusely positive for CD-34 and 70% of the SFT is positive for Bcl-2 [3]. The disease commonly arises from the thoracic cavity, yet it may arise from other sites including the kidney [2]. SFT of the kidney is an extremely rare and generally indolent tumor, unlikely to recur locally or distantly. Up to the present, only 81 cases of occurring renal SFT have been reported. SFT of the kidney usually displays a favorable prognosis and only two cases were reported to develop a distant metastasis. Furthermore local recurrence of SFT of the kidney had been reported in only one case [4]. Herein, we describe the second case of local recurrence of renal SFT after radical.

2. Case Presentation

A 50-year-old male was referred to our hospital because of a left renal mass, which had been incidentally detected by ultrasonography performed in a routine health check-up. A physical examination and blood chemical analysis were normal. Subsequent computed tomography (CT) scan detected a well-enhanced large left renal tumor (Figure 1(a)). He was diagnosed with left renal cell carcinoma preoperatively, and radical nephrectomy was performed. Grossly, the tumor was measured at 17 × 11 × 8 cm, was well-circumscribed, and displayed necrosis with a gray-white cut surface. Hemorrhage was not observed. Microscopically, the tumor was composed of spindle-shaped cells, which displayed hemangiopericytomatous patterns (Figure 2(a)). The tumor displayed normal cellularity without nuclear pleomorphism. Mitotic count was less than 1 per 10 high power fields. Immunohistochemical staining was positive for CD-34 (Figure 2(b)), Bcl-2 (Figure 2(c)), CD-99, and STAT-6, all of them representing conventional immunohistochemical markers for SFT. Meanwhile, SMA stain was negative and Ki-67 labeling index was less than 3% (Figure 2(d)). Thus, he was histologically diagnosed with SFT of the kidney without obvious malignant findings. Postoperatively, follow-up CT examination was performed regularly every 3-4 months. Three years after the operation, a mass lesion was detected in the tumor bed (Figure 1(b)). The mass lesion was increased in size after 3 months (Figure 1(c)). Fluorodeoxyglucose (FDG) positron emission tomography (PET) was ordered but the tumor did not accumulate FDG (Figure 1(d)). Nonetheless, as a local recurrence or lymph node metastasis could not be denied, we planned a surgical removal of the tumor. Although the recurrent tumor displayed spindle-shaped cells with hemangiopericytomatous patterns as in the original tumor, the cellularity was increased and cytological atypia was observed (Figure 2(e)). These results suggested an increased malignant potential of the tumor, but mitotic count was less than 4 mitoses per 10 high power fields. Immunohistochemical staining for CD-34 (Figure 2(f)), Bcl-2 (Figure 2(g)), and CD-99 all remained positive. Ki-67 labeling index was less than 15% (Figure 2(h)) and SMA stain was positive in the resected tissue from the tumor bed. Although an increased malignant potential was suggested, pathological findings did not meet the diagnostic criteria of malignant SFT [5]. The recurrent tumor was developed from an extra nodal connective tissue not from the lymph node (Figure 3). Therefore, we diagnosed local recurrence of renal SFT without evidence of obvious malignant findings. Twelve months after the second operation, the patient is followed up on the outpatient basis with no evidence of local recurrence or distant metastasis.

3. Discussion

In 1931, SFT was firstly reported as a tumor of the pleura [1]. It is a rare tumor comprising spindle-shaped cells, which might originate from mesenchymal tissue [2]. Although SFT is commonly thought of as an intrathoracic tumor, it could arise from extrathoracic organs, including the kidney [2]. Surgical resection is a standard treatment and complete resection can be associated with a favorable prognosis, even if the SFT is histologically diagnosed as malignant [4, 6].

SFT of the kidneys is a rare neoplasm, and Sasaki et al. reviewed the 68 cases of SFT in 2013 [7], and additional 13 cases were reported up to now. All reported cases, including our case, are summarized in Table 1. Most of the tumors were incidentally found with no apparent clinical symptoms. Preoperatively, most of them were diagnosed as renal cell carcinoma, and 72 out of 82 cases underwent radical nephrectomy. Mean age at diagnosis was (3–85) years and mean tumor size was (2–29) cm. Histologically, 68 tumors showed a benign appearance, whereas 11 cases exhibited a malignant one. Most patients displayed a favorable prognosis with no evidence of recurrence during the follow-up period, ranging from 0.1 to 96 months. Only 4 patients experienced recurrence; 2 patients developed distant metastasis; and 2 patients, including the present case, developed local recurrence.

Case YearAgeSexSymptomSideAffected siteTumor size
TreatmentHistology Follow-up (month) OutcomeCD-34 Authors and journals

1199648MBack pain and macrohematuriaRRenal capsule 3Nephrectomy BEN0.1DNODPOS Gelb et al. Am J Surg Pathol 20:1288
2199645FIncidental RKidney6Nephrectomy BEN8NEDPOS (2/3)Fain et al. J Urol Pathol 4:227
3199646FIncidental RKidney7.2Nephrectomy BEN33NEDPOS (2/3)Fain et al. J Urol Pathol 4:227
4199651MIncidental LKidney4.5Nephrectomy BEN2NEDPOS (2/3)Fain et al. J Urol Pathol 4:227
5199733FAbdominal pain RPeripelvis3.5Nephrectomy BEN89NEDPOSFukunaga et al. Histopathology 30:451
6199736FAbdominal pain LPeripelvis2Nephrectomy BEN12NEDPOSFukunaga et al. Histopathology 30:451
7199859MIncidental LRenal capsule NANephrectomy BENNANAPOSOokouci S et al. Jpn J Radiol 58:539
8199857MIncidental LKidney7TumorectomyBENNANAPOSTanahashi C et al. Proc Jpn Soc Pathol 87:510
9199964MMacrohematuria RKidney4.5Nephrectomy BEN8NEDPOSHasegawa et al. Hum Pathol 30:1464
10199971FIncidental LKidney9Nephrectomy BENNANANAKojima K et al. Jap-Deu Med Beriche 44:185
11200066FAbdominal pain and macrohematuriaRKidney9Nephrectomy BEN9NEDPOSLeroy et al. Urol Int 65:49
12200072FNALKidney8Nephrectomy BEN10NED POSMorimitsu et al. APMIS 108:617
13200056FIncidental LRenal capsule 5Tumor resectionBENNANANAIkeda A et al. J Hiroshima Med Assoc 53:640
14200170MIncidental RRenal pelvis 6Nephrectomy BEN60NEDPOSYazaki et al. Int J Urol 8:504
15200128FAbdominal pain LKidney15Nephrectomy BEN12NEDPOSCortes-Gutierrez et al. J Urol 166:60
16200141MMacrohematuria LKidney14Nephrectomy BEN48NEDPOSWang J et al. Am J Surg Pathol 25:1194
17200172MAbdominal discomfort RKidney13Nephrectomy BEN5NED POSWang J et al. Am J Surg Pathol 25:1194
18200257MIncidental LKidney6Nephrectomy BENNANAPOSMiyazaki N et al. Jpn Red Cross Med J 54:182
19200258MIncidental LKidneyNANephrectomy BEN9NEDNAInokawa E J Hiroshima Med Assoc 55:1057
20200231FFlank pain RKidney8.6Nephrectomy BEN8NEDPOSMagro G Pathol Res Pract 198:37
21200364FMicrohematuria RKidney4Nephrectomy BEN7NEDPOSLi S et al. Hinyokika Kiyo 49:121
22200351FNAR/LKidney25 and 2Tumor resectionBENNANANALlarena Ibarguren et al. Arch Esp Urol 56:835
23200335MNARKidney17Nephrectomy BEN6NEDNADurand X et al. Prog Urol 13:491
24200360FNARKidney11Nephrectomy BEN48NEDNABugel H et al. Prog Urol 13:1397
25200467MIncidental LKidney4.5TumorectomyBEN5NEDPOSToriyama S et al. Hinyokika Kiyo 50:138
26200483MNARKidney9Nephrectomy BEN18NEDPOSGres P et al. Prog Urol 14:65
27200453MFlank pain and swellingRRenal capsule 14Tumor resectionBEN36DNODPOSKunieda K et al. Surg Today 34:90
28200459MIncidental LRenal capsule 6.8Nephrectomy BEN48NEDPOSYamada H et al. Pathol Int 54:914
29200529NAIncidental NAKidney2.2Nephrectomy BENNANAPOSPierson DM et al. Mod Pathol 18:159
302005NANAIncidental NAKidneyNANephrectomy BENNANAPOSPierson DM et al. Mod Pathol 18:160
312005NANAIncidental NAKidneyNANephrectomy BENNANAPOSPierson DM et al. Mod Pathol 18:161
322005NANAIncidental NAKidneyNANephrectomy BENNANAPOSPierson DM et al. Mod Pathol 18:162
332005NANAIncidental NAKidneyNANephrectomy BENNANAPOSPierson DM et al. Mod Pathol 18:163
342005NANAFlank painNAKidneyNANephrectomy BENNANAPOSPierson DM et al. Mod Pathol 18:164
35200579NAFlank painNAPerirenal10.1Nephrectomy BENNANAPOSPierson DM et al. Mod Pathol 18:165
36200551FFlank painNARenal capsule 10Nephrectomy BENNANAPOSYamaguchi T Urology 65:175
37200551FFever elevation RRenal capsule 13Nephrectomy BENNANAPOS (focal)Jhonson TR et al. J Comput Assist Tomogr 29:481
38200583FIncidental LKidney11Nephrectomy BENNANAPOSKawagoe M Nishinihon J Urol 67:568
39200676MIncidental LKidney12Nephrectomy MAL4Lung metastasis POS (benign site)Fine SW et al. Arch Pathol Lab Med 130:857
40200618FFlank pain LKidney3Nephrectomy BEN15NEDPOSKoroku M et al. Hinyokika Kiyo 52:705
4120064MNARKidney8Nephrectomy BENNANANAProvance et al. Clin Pediatr 45:871
42200685MFlank pain LKidney4.5Nephrectomy BENNANAPOSKohl SK et al. Arch Pathol Lab Med 130:117
43200654MIncidental RKidneyNANephrectomy BEN16NED POSTanaka M et al. Hinyokika Kiyo 52:79
44200636MFlank pain RKidneyNANephrectomy BENNANANAAlvarez Mugica M et al. Arch Esp Urol 59:195
45200726MIncidental RKidney7Nephrectomy BEN6NEDPOSConstantinidis C et al. The Can J Urol 14:3583
46200770MFlank pain and macrohematuriaLKidney15Nephrectomy BEN6NEDPOSZnati K et al. Revies in Urol 9:36
47200751FFlank pain LKidney4Nephrectomy BEN10NEDPOSBozkurt SU et al. APMIS 115:259
48200766FAbdominal mass and macrohematuriaRKidney11Nephrectomy BENNANANAKakoi N et al. Japn J Urol Surg 20 supple 598
49200760sMIncidental RKidney3Nephrectomy BEN3NEDNAYoshida T et al. Hinyokika Kiyo 53:745
50200834FFlank pain LKidney9Nephrectomy MAL21NEDPOSMagro G et al. APMIS 115:1020
51200867MMacrohematuria LKidney7Nephrectomy BEN10NEDPOSAmano T et al. Hinyokika Kiyo 54:357
52200844FIncidental LKidney5.8Nephrectomy BEN40NEDPOSHirabayashi J et al. Hinyokika Kiyo 54:357
53200975FIncidental LKidney4.5Nephrectomy BEN9NEDPOSHirano D et al. Mod Mol Morphol 42:239
54200964FCoughLKidney2.5Biopsy BEN12NEDPOSPetrella F et al. Minerca Chir 64:669
55200935MIncidental RKidney8Partial nephrectomy BENNANAPOSMakris A et al. Can J Urol 16:4854
56200972FAbdominal massLKidney19Nephrectomy MALNANANAMarzi M et al. Urologia 76:112
57200976FIncidental RKidney2.5Nephrectomy BEN48NEDPOSYoneyama T et al. Hinyokika Kiyo 55:479
58200950MIncidental LKidney5.5Nephrectomy BENNANEDPOSMatsumoto T et al. Japn J Urol Surg 22:230
59200963MIncidental LKidney5.3Nephrectomy MALNANAPOSMurayama S et al. Japn J Urol Surg 22:230
60200951FIncidental RKidney12Nephrectomy BENNANAPOSOgushi S et al. Japn J Urol Surg 22:230
61200975MNALKidney3Nephroureterectomy BENNANAPOSKobori Y et al. Hinyokika Kiyo 55:305
62201039MDysuriaLKidney25Nephrectomy BEN12NEDPOSTaza L et al. Actas Urol Esp 34:568
63201039FAbdominal fullness LKidney20Embolization and nephrectomy BEN6NEDPOSYamaguchi Y et al. Hinyokika Kiyo 56:435
64201144MMacrohematuriaLKidneyNAEmbolization and nephrectomy BENNANANASaegusa M et al. Nishinihon J Urol 68:187
65201152FAbdominal painRKidney18Nephrectomy and thrombectomyBEN6NEDPOSNaveen HN et al. Urol Ann 3:158
66201172FAbdominal massLKidney19Nephrectomy MAL15NEDPOS (focal)Marzi M et al. Minerva Urol Nephrol 63:109
67201150FFlank pain RKidney15Nephrectomy MAL30NEDPOSTsan-Yu Hsieh Diag Pathol 6:96
68201268FFlank painNAKidneyNANephrectomy MALNANAPOSM. de Martino Aktuel Urol 2012; 43(01):59–62
69201272MFlank painLKidney7Nephrectomy MAL45NEDPOSSfoungaristos S Prague Med Rep/Vol 113 No. 3, 246–250
70201256MShortness of breathLKidney10, 10Nephrectomy MAL10NEDPOSG. Zhao et al. Oncology Letters 4:993–995, 2012
71201349F DyspneaLKidneyNANephrectomy BEN23SDPOSJ. Cuello et al. Case Rep Oncol Med 2013; 2013:564980
72201348MAbdominal massRKidney29Nephrectomy BEN96NEDPOS (55%)Sasaki H et al. Case Rep Nephrol Urol 3:1–8
73201357MLumbar painLKidney14Nephrectomy BEN26NED POSAbdullah D et al. Case Report in Urol 147496:4
7420133MNANAKidneyNANephrectomy NANANANAWu WW et al. Int J Surg Pathol 23(1):34–47
75201349FFever elevation and flank painRKidney5Nephrectomy BENNANEDPOSNazih K et al. Urol Int 2013; 91:373–383
76201343MAcute recurrent pancreatitisNAKidneyNANANANANANAPatel YA et al. Pancreatology 13(6):631–3
77201330FNANARenal pelvis NANephrectomy BENNANANAPathak TB et al. JNMA Apr-Jun; 52(190):388–90
78201466FFlank massRKidney26Nephrectomy MAL9NEDPOS > NEGWang et al. Diagnostic Pathol 9:13
79201419FHematuriaLKidney14.5Embolization and nephrectomy MAL30NEDPOSEttore M et al. Onco Targets and Therapy Jul 679–685
80201435FBack painLKidney3Nephrectomy BEN15NEDPOSJie Ma et al. Int J Clin Exp Pathol 7(7):4268–4237
81201455NANANAKidneyNANephrectomy NANANANATritschler P et al. JBR-BTR Sep-Oct; 97(5):298–300
82our case50MIncidental LKidney17Nephrectomy BEN36LRPOS

M, male; F, female; NA, not available; R, right; L, left; BE, benign; MAL, malignant; DNOD, died not of disease; NED, no evidence of disease; SD, stable disease; LR, local recurrence; POS, positive.
CD-34 immunoreactivity (the extent of positive area is shown in parentheses, if information is available).

As SFT commonly expresses CD-34, Bcl-2, and CD-99 [8], these surface antigens can serve as useful diagnostic markers [8]. And negativity in CD-34 and Bcl-2 reportedly represents increased malignant potential [8, 9]. Fine et al. documented a case of malignant renal SFT without expressing CD-34, which developed distant metastasis four months after surgery [10]. We also reported a similar case previously, which did not express CD-34 and went on to metastasize to the lung and liver [7]. In that case, half of the cross section area of the primary tumor was positive for CD-34, while the remaining area was negative for it. The patient developed distant metastases 8 years after nephrectomy. Resection of the metastatic tumors had revealed that CD-34 was totally absent in the tumors. Thus, the loss of CD-34 staining in SFT of the kidney may promote tumor metastasis to other organs [7]. Similarly to CD-34 staining, Bcl-2 staining was commonly observed in SFT and the loss of Bcl-2 staining was reported to be associated with malignant potential in retroperitoneal SFTs [9].

On the contrary, malignant potential is rather low in the present case, which developed local recurrence 3 years after nephrectomy. In this case, no obvious malignant findings were observed in either primary or recurrent tissue from the tumor bed. Furthermore, CD-34 and Bcl-2 were positive in the primary tumors and remained positive in the recurrent tissue. It seems that the local recurrence does not necessarily accompany the loss of expression of CD-34 and Bcl-2, and another explanation for unpredicted local recurrence would be incomplete resection at surgery [5]. However, from a different standpoint, the tumor in the present case may have had a great tendency to local recurrence, as the tumor accompanies multiple clinical features such as extrathoracic location, large tumor size, increased cellularity, and presence of necrosis among the risk factors for local recurrence described by Jason et al. [11].

Overall, we believe that there is no strict dichotomy between benign and malignant SFTs and that all tumors likely have some degree of metastatic potential, albeit quite low. Therefore, although renal SFT is thought to be a benign tumor, an adequate follow-up period is required to evaluate the precise clinical outcome of renal SFT, and the follow-up period in this report of 82 patients may not be sufficient (Table 1). Furthermore, most reported renal SFTs were large in size at the diagnosis and it might be leading cause of missing the malignant features in whole tumor tissue. We should also concern this issue for evaluating the real feature of renal SFTs in future.

FDG accumulation was not observed within the tumor on FDG-PET. To date, there is no reported association between SFTs and FDG accumulation, and our result suggests that PET-CT may be invalid. Further detailed examination is also required to clarify this point.

In conclusion, a case of SFT of the kidney exhibiting local recurrence was reported. In our case, no obvious malignant findings were observed in either the primary tumor or the recurrent tumor. Loss of expression in CD-34 and Bcl-2, which is closely associated with malignant potential, was not observed. Although SFT of the kidney usually displays a favorable clinical course, careful and sufficient follow-up may be required even in the absence of malignant findings.

The patient described in the case report has given his informed consent for the case report to be published.

Competing Interests

The authors declare that there is no conflict of interests regarding the publication of this paper.


  1. P. Klemperer and C. B. Rabin, “Primary neoplasm of the pleura: a report of five cases,” Archives of Pathology & Laboratory Medicine, vol. 11, pp. 385–412, 1931. View at: Google Scholar
  2. J. R. Goodlad and C. D. M. Fletcher, “Solitary fibrous tumour arising at unusual sites: analysis of a series,” Histopathology, vol. 19, no. 6, pp. 515–522, 1991. View at: Publisher Site | Google Scholar
  3. G. T. MacLennan and L. Cheng, “Solitary fibrous tumor of the kidney,” Journal of Urology, vol. 181, no. 6, pp. 2731–2732, 2009. View at: Publisher Site | Google Scholar
  4. S. Sfoungaristos, M. Papatheodorou, A. Kavouras, and P. Perimenis, “Solitary fibrous tumor of the kidney with massive retroperitoneal recurrence. A case presentation,” Prague Medical Report, vol. 113, no. 3, pp. 246–250, 2012. View at: Google Scholar
  5. D. M. England, L. Hochholzer, and M. J. McCarth, “Localized benign and malignant fibrous tumors of the pleura. A clinicopathologic review of 223 cases,” The American Journal of Surgical Pathology, vol. 13, no. 8, pp. 640–658, 1989. View at: Google Scholar
  6. Y. Morimitsu, M. Nakajima, M. Hisaoka, and H. Hashimoto, “Extrapleural solitary fibrous tumor: clinicopathologic study of 17 cases and molecular analysis of the p53 pathway,” APMIS, vol. 108, no. 9, pp. 617–625, 2000. View at: Publisher Site | Google Scholar
  7. H. Sasaki, T. Kurihara, Y. Katsuoka et al., “Distant metastasis from benign solitary fibrous tumor of the kidney,” Case Reports in Nephrology and Urology, vol. 3, no. 1, pp. 1–8, 2013. View at: Publisher Site | Google Scholar
  8. T. Yokoi, T. Tsuzuki, Y. Yatabe et al., “Solitary fibrous tumour: significance of p53 and CD34 immunoreactivity in its malignant transformation,” Histopathology, vol. 32, no. 5, pp. 423–432, 1998. View at: Publisher Site | Google Scholar
  9. I. Takizawa, T. Saito, Y. Kitamura et al., “Primary solitary fibrous tumor (SFT) in the retroperitoneum,” Urologic Oncology: Seminars and Original Investigations, vol. 26, no. 3, pp. 254–259, 2008. View at: Publisher Site | Google Scholar
  10. S. W. Fine, D. M. McCarthy, T. Y. Chan, J. I. Epstein, and P. Argani, “Malignant solitary fibrous tumor of the kidney: report of a case and comprehensive review of the literature,” Archives of Pathology and Laboratory Medicine, vol. 130, no. 6, pp. 857–861, 2006. View at: Google Scholar
  11. J. S. Gold, C. R. Antonescu, C. Hajdu et al., “Clinicopathologic correlates of solitary fibrous tumors,” Cancer, vol. 94, no. 4, pp. 1057–1068, 2002. View at: Publisher Site | Google Scholar

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