Laparoscopic Non-clamping Tumor Enucleation of Renal Hilum Schwannoma in a Single Kidney: A Case Report.

A 56-year-old woman underwent laparoscopic right nephrectomy due to pyonephrosis associated with right ureteral stones. Moreover, the patient developed a brain stem hemorrhage and became bedridden. At the time of nephrectomy, a renal tumor, with a size of 24 × 24 × 20 mm, was observed in the left renal hilum; the tumor did not show contrast enhancement on computed tomography. After 3 years, the tumor gradually grew to a size of 45 × 35 × 34 mm, and therefore, laparoscopic non-clamping tumor enucleation was performed. Pathological examination confirmed a diagnosis of renal schwannoma.

Introduction

Laparoscopic partial nephrectomy is widely used as the first line of treatment for T1a renal tumors; however, this procedure involves many technical limitations. Moreover, the presence of a tumor in the renal hilum, especially in a patient with a single kidney, requires careful operation by a highly skilled surgeon. In such cases, non-clamping partial nephrectomy may be used to conserve renal function; however, this surgery is even more challenging.

Schwannomas are known to occur frequently in the head, neck, hands, and feet. Renal schwannomas are rare; they are generally diagnosed on pathological examination since their preoperative diagnosis is difficult.

Here, we report a case of renal hilum schwannoma in a patient with a single kidney that was treated by laparoscopic non-clamping tumor enucleation, and present a review of the relevant literature.

Case presentation

A 56-year-old woman underwent laparoscopic right nephrectomy due to pyonephrosis associated with right ureterolithiasis; furthermore, she developed a brain stem hemorrhage and became bedridden before this time. During nephrectomy, a renal tumor measuring 24 × 24 × 20 mm, was observed in the left renal hilum; on computed tomography (CT), the tumor lacked contrast enhancement (Fig. 1). However, due to the presence of uncontrolled pyonephrosis, right nephrectomy was emergently performed. Postoperative laboratory examination results were almost within normal limit, except for slight renal dysfunction. The tumor grew slowly during follow-up, reaching a size of 45 × 35 × 34 mm after 3 years. The tumor size continued to increase, and we anticipated that its continued growth could cause severe renal dysfunction. The serum creatinine level gradually increased and was >1.0 mg/dL at the preoperative stage. The patient refused hemodialysis and chose surgical resection.

Figure 1

Above: Preoperative computed tomography (CT) shows a left renal hilum mass (24 × 24 × 20 mm) showing no contrast enhancement. Below: Postoperative CT shows no evidence of local recurrence or distant metastasis 3 months postoperatively.

Partial nephrectomy was chosen to preserve renal function since the patient had only a single kidney (subsequent to right nephrectomy for pyonephrosis). It was performed without clamping the renal vessels due to further preserve renal function. Renal hilum exfoliation revealed a part of the tumor; further dissection of the renal parenchyma allowed the identification of the entire tumor, which separated completely from the renal parenchyma. The tumor was excised gradually by blunt dissection from the renal parenchyma, followed by closure of the urinary tract and renorraphy. Since the tumor was present in the renal hilum, the renal parenchyma was incised through the renal hilum using a sealing device (Plasma Kinetic system: GYRUS). This exposed the tumor front (Fig. 2). The intraoperative bleeding volume was 510 mL, and the operation time was 210 min. No postoperative complications were noted.

Figure 2

The tumor was present in the renal hilum; the renal parenchyma was incised to create a double-opening from the hilum using a sealing device.

No evidence of local recurrence or distant metastasis was noted on imaging studies performed 5 months postoperatively, and CT findings confirmed adequate function of the renal parenchyma. Continued follow-up imaging studies have been planned. Biochemical tests revealed no changes in the degree of renal dysfunction as compared to the preoperative status. The preoperative serum creatinine level was approximately 1.0 mg/dL; postoperatively, it was approximately 1.2 mg/dL.

Macroscopically, the excised tumor was solid and yellow; further examination revealed a cystic appearance within. Histopathological examination revealed interlacing fascicles of spindle cells (Antoni A) (Fig. 3). S-100 immunostaining showed a positive reaction in the tumor cells.

Figure 3

Left side: Microscopic examination (×200) shows interlacing fascicles of schwannoma spindle cells. Right side: Immunostaining with S-100 antibody (×100) shows a diffuse positive reaction on the tumor cells.

Discussion

Although schwannomas are typically found in the head, neck, and limbs, they may also develop in other parts of the body. Retroperitoneal schwannomas are rare, accounting for 1–3% of all cases of schwannomas; moreover, retroperitoneal schwannomas account for only 1% of cases of retroperitoneal tumors. Only a few cases of retroperitoneal schwannomas have been reported, and reports of renal retroperitoneal schwannomas are even rarer. A PubMed search revealed 24 reports (comprising a total of 30 patients) of renal schwannoma in English publications (Table 1).

Table 1

Summary of renal schwannoma cases reported in the English literature

Author	Year	Age (years)	Sex	Symptoms	Side	Treatment	Size (cm)	Location	Malignancy
Phillips	1955	56	M	Flank pain	L	Nephrectomy	12	Pelvis	No
Fein	1965	51	F	Recurrent pyelonephritis, palpable mass	R	Nephrectomy	6	Pelvis	No
Romics	1978	56	M	Microhematuria	R	Nephrectomy	7	Hilum	No
Steers	1985	50	F	Palpable mass	R	Tumorectomy	9	Hilum	No
Somers	1988	55	F	Incidental findings	L	Nephrectomy	5.1	Parenchyma	No
Kitagawa	1990	51	M	Upper abdominal pain and high fever	L	Nephrectomy	2.8	Hilum	No
Ma	1990	67	M	Epigastric pain	R	Nephrectomy	8	Parenchyma	No
Naslund	1991	50	F	Anemia, weight loss	L	Nephrectomy	14	Parenchyma	Yes
Romics	1992	52	M	Back and flank pain	R	Nephrectomy	NR	Capsule	Yes
Ikeda	1996	89	M	Abdominal pain	R	Nephrectomy	NR	Pelvis	No
Singer	1996	70	F	Incidental finding	L	Nephrectomy	6	Hilum	No
Pantuck	1996	50	F	Palpable mass	R	Nephrectomy	28	Capsule	Yes
Alvarado-Cabrero	2000	18	F	Flank pain	R	Nephrectomy	6.2	Parenchyma	No
Alvarado-Cabrero	2000	84	M	Incidental finding	R	Nephrectomy	4	Parenchyma	No
Alvarado-Cabrero	2000	40	F	Flank pain, abdominal mass	L	Nephrectomy	12.5	Parenchyma	No
Alvarado-Cabrero	2000	45	M	Flank and abdominal pain	L	Nephrectomy	16	Parenchyma	No
Tsurusaki	2001	69	F	Incidental finding	L	Tumorectomy	NR	Capsule	No
Cachay	2003	74	F	Incidental finding	R	Nephrectomy	9	Capsule	Yes
Singh	2005	40	M	Renal colicky pain, vomiting	L	Nephrectomy	3	Hilum	No
Singh	2005	35	M	Flank pain, gross hematuria	R	Nephrectomy	NR	Pelvis	No
Tokunaga	2005	39	F	Incidental finding	R	Nephrectomy	8	Hilum	No
Hung	2007	36	F	Palpable mass, flank pain	L	Nephrectomy	7	Parenchyma	No
Gobbo	2008	59	F	Incidental finding	L	Nephrectomy	4.8	Hilum	No
Gobbo	2008	27	F	Incidental finding	R	Nephrectomy	8.5	Parenchyma	No
Gobbo	2008	35	F	Flank and abdominal pain, nausea	L	Nephrectomy	7	Hilum	No
Sfoungaristos	2011	55	F	Incidental finding	L	Nephrectomy	2.8	Hilum	No
Yang	2012	40	F	Flank pain	L	Nephrectomy	6.8	Pelvis	No
Himabindu	2012	36	F	Flank pain	R	Nephrectomy	4.6	Parenchyma	No
Verze	2013	59	M	Incidental finding	R	Nephrectomy	15	Parenchyma	No
Himabindu	2013	36	F	Flank pain, fever	R	Tumorectomy	4.6	Parenchyma	No
Present case	2015	63	F	Incidental findings	L	Tumorectomy	2.4	Hilum	No

NR: Not reported.

Renal schwannomas are difficult to diagnose preoperatively on the basis of clinical symptoms and radiographic findings; thus, they are often diagnosed based on the results of pathological examinations. In recent years, as diagnostic imaging techniques have improved, schwannomas are commonly diagnosed as an incidental finding.

Regardless of whether a schwannoma is benign or malignant, this tumor typically does not cause symptoms and grows slowly. Therefore, the diagnosis of schwannoma may become difficult due to the presence of metastasis and direct invasion at the time of the diagnosis.

Under light microscopy, the typical tumor pattern of a schwannoma includes Antoni A and Antoni B areas. S-100 immunostaining may be useful for the differential diagnosis of malignant tumors, as positive staining is specific to neoplasms arising from the neural crest and melanomas.2, 3, 4

Preoperatively, it is impossible to distinguish between benign and malignant schwannomas given the similarity in their appearance; furthermore, it is believed that surgical resection is the only effective treatment for renal schwannomas. Almost all the patients described in the reviewed literature underwent nephrectomy or radical nephrectomy; only 4 reported cases (including the present case) underwent tumorectomy, and this treatment was employed primarily due to the specific tumor size and location.

Imao et al cite the first laparoscopic surgery by Furuse et al for resecting retroperitoneal schwannoma in 1995; since then, the use of laparoscopic surgery has continued to increase. Among the cases treated by laparoscopic resection (Table 1), none were definitively diagnosed as schwannoma preoperatively. Moreover, the average bleeding volume and operation time were 120 mL and 200 min, respectively, and there were no perioperative or postoperative complications in any of the reported cases. In the present case, considering the non-clamping resection along with incision of renal parenchyma, the intraoperative bleeding volume of 510 mL was not significantly higher than that in previous reports.

In our hospital, non-clamping partial nephrectomy has been performed since 2013. In the present patient, there were no obvious perioperative or postoperative complications. Thus, non-clamping resection of renal tumors may be considered a safe treatment option, especially for tumors with clear capsules.

Conclusion

In conclusion, non-clamping laparoscopic enucleation may be feasible even for a renal hilum tumor, such as the rare entity of a renal schwannoma, in a patient with a single kidney.

Consent

The study participant provided informed consent.

Conflicts of interest

None declared.