British Journal of Medical and Surgical Urology (2012) 5, 184—187
Benign renal Schwannoma: Case report and review of the literature J.A. Raju a,∗, G. Kingston b, A. Jones c a
Department of Urology, Royal Berkshire Hospital NHS Foundation Trust, Reading, United Kingdom Department of Histopathology, Royal Berkshire Hospital NHS Foundation Trust, Reading, United Kingdom c Department of Urology, Royal Berkshire Hospital NHS Foundation Trust, Reading, United Kingdom b
Received 4 March 2011 ; received in revised form 1 November 2011; accepted 2 November 2011
KEYWORD Benign renal Schwannoma
Schwannomas are tumours originating from Schwann cells of nerve sheaths and are most commonly found in the head, neck, limbs and mediastinum. They are typically benign but in rare cases can demonstrate malignant change . Retroperitoneal Schwannomas are uncommon, accounting for 0.3—3.2% of cases  while visceral involvement is even rarer. Only 21 cases of benign renal Schwannoma have been reported [1,3,4]. We present the clinico-pathological features of an additional case and review the literature.
A 38 year old lady presented with right sided colicky pain which was investigated with non-contrast CT. This showed no calculi but a 36 mm, partly exophytic, soft tissue mass was noted in the hilar region of the left kidney, which was suspicious for renal cell carcinoma (Fig. 1). Urine cytology was negative for malignant cells. Staging CT demonstrated no metastases. The patient underwent laparoscopic radical nephrectomy one week later. Our patient remains well 18 months post surgery. Macroscopically three well circumscribed yellow-white nodules with a whorled appearance were seen, each measuring 7, 9 and 22 mm in maximum dimension. Microscopically the tumours were well-circumscribed encapsulated spindle cell lesions with no cellular atypia. Features in keeping with the diagnosis of Schwannoma are demonstrated in Figures 2 and 3. Conﬁrmatory immunohistochemistry showed the lesional cells to be positive for S100 (Fig. 4) and negative for desmin, actin, HMB-45, melanA and cytokeratin.
Corresponding author. Tel.: +44 118 3228551. E-mail addresses: [email protected]
(J.A. Raju), [email protected]
(G. Kingston), [email protected]
1875-9742/$ — see front matter © 2011 British Association of Urological Surgeons. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.bjmsu.2011.11.003
Benign renal Schwannoma
Figure 3 Haematoxylin and eosin section (×100) demonstrating a cellular Antoni A area (bottom half) merging with a looser Antoni B area (top half).
Figure 1 Coronal CT image demonstrating a 36 mm soft tissue mass within the hilar region of the left kidney.
Adjacent kidney and resection margins were unremarkable and there was no evidence of malignancy.
Discussion Renal Schwannomas are extremely rare (Table 1) [1,3,4] and because they tend to be benign and
Figure 2 Haematoxylin and eosin section (×100) highlighting parallel arrays of spindle cells showing palisading of bland nuclei, with intervening parallel bands of eosinophilic cytoplasmic processes. This effect results in the formation of characteristic Verocay bodies.
slow growing they have a non-speciﬁc presentation. Common sites of tumour include the renal parenchyma, pelvis and capsule. Flank pain is a common complaint and may be the only symptom described. In our patient the pain was on the contralateral side and was unlikely to have been directly related to the tumour. Less common presentations include haematuria and fever, while in many cases Schwannomas are found incidentally . CT and MRI have a role in characterising retroperitoneal masses  but, as in our case, the differentiation of benign and malignant renal masses is difﬁcult and a histological diagnosis should always be sought. CT-guided needle biopsies of retroperitoneal neural sheath tumours have been shown to be inaccurate or inconclusive . Likewise the accuracy of renal biopsies for renal cell carcinomas can still leave an element of doubt.
Figure 4 S100 immunohistochemistry demonstrates strong diffuse expression (which is both nuclear and cytoplasmic). This appearance is typical of a Schwannoma.
Reported cases of benign renal schwannoma [1,3,4].
Follow up (months)
5 — NED
Nephrectomy Tumour excision
18 — NED NA
Generalised malaise, weight loss, fever, ﬂank pain Generalised malaise, weight loss, fever, ﬂank mass Hypertension, microscopic haematuria, renal impairment Microscopic haematuria, ﬂank mass Incidental Upper abdominal pain, fever Epigastric pain
12 — NED
Ikeda Singer Alvardo-Cabrero Alvardo-Cabrero Alvardo-Cabrero
1996 1996 2000 2000 2000
89 70 45 40 84
M F M F M
R L L L R
NA 6 16 12.5 4
Parenchyma & pelvis Pelvis Hilum Parenchyma Parenchyma Parenchyma
Schwannoma Schwannoma Ancient Schwannoma Schwannoma Schwannoma
Nephrectomy Nephrectomy Nephrectomy Nephrectomy Nephrectomy
NA 18 — 60 — 12 — 54 —
Alvardo-Cabrero Tsurusaki Singh Singh
2000 2001 2005 2005
18 69 40 35
F F M M
R L L R
6.2 NA 3 NA
Parenchyma Hilum Hilum Hilum
Schwannoma Schwannoma Schwannoma Schwannoma
Nephrectomy Tumour excision Nephrectomy Nephrectomy
42 — NED NA 36 — NED 12 — NED
Umphrey  Hung  Gobbo Gobbo Gobbo Present case
2007 2008 2008 2008 2008 2010
63 36 59 27 35 38
F F F F F F
R L L R L L
7 7 4.8 8.5 7 3.6
Parenchyma Parenchyma Hilum Parenchymal Hilum Parenchyma
Schwannoma Schwannoma Schwannoma Ancient Schwannoma Schwannoma Schwannoma
Nephrectomy Nephrectomy Nephrectomy Nephrectomy Nephrectomy Nephrectomy
12 — NED 6 — NED NA 8 — NED 4 — NED 18 — NED
NA: not available; NED: no evidence of disease.
NED NED NED NED
J.A. Raju et al.
Abdominal pain Incidental Flank and abdominal pain Flank pain Found during work up of cystitis Flank pain Incidental Renal colic pain, vomiting Flank pain, visible haematuria Hypertension, hot ﬂushes Flank pain, palpable mass Incidental Incidental Abdominal pain, nausea Incidental. Contralateral side ﬂank pain
Benign renal Schwannoma
The histological differential diagnosis of benign Schwannoma includes malignant peripheral nerve sheath tumour, angiomyolipoma, leiomyoma, sarcomatoid renal cell carcinoma and other rare mesenchymal renal tumours . Immunostaining for S-100 protein, positive in tumours arising from the neural crest and melanoma, is useful in differentiating Schwannoma from these other tumours. Malignant change of benign Schwannomas is very rare [1,2] and therefore excision of the tumour will be curative in virtually all cases.
Conclusion Our case highlights the difﬁculty in differentiating renal cell carcinoma from the rarer benign tumours preoperatively. We suggest therefore that the treatment of choice in patients with suspicious renal masses must be partial or radical nephrectomy. A small proportion of these will have rare
benign masses and patients must be aware of this risk preoperatively.
Conﬂict of interest statement The authors declare that there are no conﬂicts of interest.
References  Gobbo S, Eble JN, Huang J, Grignon D, Wang M, Martignoni G, et al. Schwannoma of the kidney. Modern Pathology 2008;21:779—83.  Schindler OS, Dixon JH, Case P. Retroperitoneal giant Schwannomas: report on two cases and review of the literature. Journal of Orthopaedic Surgery 2002;10:77—84.  Umphrey HR, Lockhart ME, Kenney PJ. Benign renal Schwannoma. Radiology Case Reports 2007;2:52—5.  Hung SF, Chung SD, Lai MK, Chueh SC, Yu HJ. Renal schwannoma: case report and literature review. Urology 2008;72, 716.e3-.e6.  Guz BV, Wood DPJ, Montie JE, Pontes JE. Retroperitoneal neural sheath tumors: Cleveland clinic experience. Journal of Urology 1989;142:1434—7.
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