- Email: [email protected]
Melanotic Schwannoma: A Case of Renal Origin
Case Report
Melanotic Schwannoma: A Case of Renal Origin Paolo Verze,1 Anna Somma,2 Ciro Imbimbo,1 Gelsomina Mansueto,2 Vincenzo Mirone,1 Luigi Insabato2 Clinical Practice Points Schwannomas are uncommon tumors that originate
Melanotic schwannoma is a rare variant probably
from the Schwann cells of the peripheral nerve sheath and are exceedingly rare in the kidneys. We report on a case of an incidental large renal tumor which was diagnosed as melanotic schwannoma. To the best of our knowledge this is the first case of renal origin reported.
caused by the neoplastic proliferation of a common precursor cell for Schwann cells and melanocytes and can develop a potentially malignant clinical behavior.
Clinical Genitourinary Cancer, Vol. 12, No. 1, e37-41 ª 2014 Elsevier Inc. All rights reserved. Keywords: Kidney tumor, Melanotic, Rare variant, Renal mass, Schwannoma
Case Report A 59-year-old man, otherwise healthy, was discovered to be affected with a large mass of the right kidney during an occasional 1 Department of Neurosciences, Sciences of Reproduction and Odontostomatology, Urology Unit 2 Department of Biomorphological and Functional Science, Anatomic Pathology Unit, University of Naples “Federico II,” Naples, Italy
Submitted: Jul 5, 2013; Revised: Sep 6, 2013; Accepted: Sep 24, 2013; Epub: Sep 28, 2013 Address for correspondence: Paolo Verze, MD, PhD, Via Sergio Pansini, 5, 80131 Naples, Italy Fax þ39-0817464311; e-mail contact: [email protected]
Figure 1 Computed Tomography Scan Showed a Tumor Localized at Upper Pole of the Kidney With Concomitant Downward Displacement of Renal Hilum
1558-7673/$ - see frontmatter ª 2014 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.clgc.2013.09.005
abdominal ultrasound while undergoing a spontaneous health checkup visit. He had no urologic symptoms. A multiphase computed tomography (CT) scan using a GE 64-slice multi detector computed tomography was performed. The CT scan revealed a 12 10 cm renal tumor located at the upper pole of the kidney with concomitant downward displacement of the renal hilum. After contrast injection, during the arterial phase the mass showed a contrast enhancement directly supplied through an additional polar branch of the renal artery. Furthermore, large central necrotic areas were detected (Fig. 1). Despite its large size, the mass was not compressing the ureter and not cause hydronephrosis. The workup was within normal limits. Preoperative tumor stage assessment was
Figure 2 The Cut Surface of the Renal Mass Showed Areas of Hemorrhage, and Cystic Change
Clinical Genitourinary Cancer February 2014
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Investigator
Year
Age, Years
Sex
Side
Treatment
Size (cm) / Gross
Location
Diagnosis
Malignancy
Patient Status (Follow-Up)
Phillips2
1955
56
M
L
Left nephrectomy
12-cm Encapsulated tumor
Pelvis
Schwannoma
No
NR
Kuz’mina3
1962
33
F
R
Right nephrectomy
Encapsulated rubbery, pale gray tumor
Capsule
Schwannoma
No
NR
Fein4
1965
51
F
R
Right nephrectomy
6-cm Well encapsulated mass
Pelvis
Schwannoma
No
Alive (24-month)
Bair5
1978
56
M
R
Right nephrectomy
7-cm Mass
Hilum
Schwannoma
No
Alive (5-month)
Steers6
1985
50
F
R
Tumorectomy
9-cm multicystic mass
Hilum
Schwannoma
No
Somers7
1988
55
F
L
Left nephrectomy
No
L
Left nephrectomy
Intraparenchymal upper pole Hilum
Schwannoma
Upper abdominal pain and high fever
Cellular schwannoma
NR
NR
M
Epigastric pain
R
Right nephrectomy
No
Alive (1-year)
F
L
Left nephrectomy
Malignant schwannoma
Yes
Died after 15 months
1992
52
M
R
Right nephrectomy
Large infiltrating mass
Capsule
Malignant schwannoma
Yes
Died after 3 months
Ikeda12 Singer13
1996 1996
89 70
M F
Anemia, mild abdominal discomfort, weight loss Back and flank pain, fever, anemia Abdominal pain Asymptomatic
Intraparenchymal and pelvis Intraparenchymal upper pole
Cellular schwannoma
50
5.1-cm Well defined solid lobular mass 2.8-cm Well demarcated yellowish tumor 8-cm Well encapsulate yellowish tumor 14-cm Mass
Kitagawa8
1990
51
M
Ma9
1990
67
Naslund10
1991
Romics11
R L
Right nephrectomy Left nephrectomy
Pelvis Hilum
Schwannoma Schwannoma
No No
NR Alive (18-month)
Pantuck14 AlvaradoCabrero15 AlvaradoCabrero15 AlvaradoCabrero15
1996 2000
50 18
F F
Palpable mass Flank pain
R R
Right nephrectomy Right nephrectomy
NR 6-cm Well demarcated mass 28-cm Mass 6.2-cm Mass
Perirenal Intraparenchymal
Malignant schwannoma Schwannoma
Yes No
Died after 42 months Alive (42-month)
2000
84
M
Incidental finding
R
Right nephrectomy
4-cm Mass
Intraparenchymal
Cellular schwannoma
No
Alive (54-month)
2000
40
F
L
Left Nephrectomy
12.5-cm Mass
Intraparenchymal
Cellular schwannoma
No
Alive (12-month)
AlvaradoCabrero15
2000
45
M
Flank pain, fever, abdominal mass, anemia Flank and abdominal pain
L
Left Nephrectomy
16-cm Mass
Intraparenchymal
Ancient schwannoma
No
Alive (60-month)
Symptoms Generalized malaise, weight loss, fever, flank pain, mild anemia Generalized malaise, weight loss, mild fever, flank mass Recurrent pyelonephritis, palpable mass, pyuria Hypertension, microhematuria Microhematuria, palpable mass Incidental findings
NR Alive (18-month)
Melanotic Schwannoma: A Case of Renal Origin
Clinical Genitourinary Cancer February 2014
Table 1 Summary of Data From All Reported Cases
Table 1 Continued Investigator
Year
Age, Years
Sex
Tsurusaky16
2001
69
F
Incidental finding
L
Tumorectomy
Cachay17
2003
74
F
Asymptomatic
R
Singh18
2005
40
M
Singh18
2005
35
M
Hung1 Gobbo19 Gobbo19
2007 2008 2008
36 59 27
F F F
Renal colicky pain, vomiting Flank pain, gross hematuria Palpable mass, flank pain Asymptomatic Incidental finding
Gobbo19
2008
35
F
Verze (present case)
2013
59
M
Symptoms
Side
Treatment
Size (cm) / Gross
Location
Diagnosis
Malignancy
Patient Status (Follow-Up) NR
Capsule
Schwannoma
No
Right nephrectomy
White mass with necrosis 9-cm Mass
Perirenal
Malignant schwannoma
Yes
L
Left nephrectomy
3-cm Firm mass
Hilum
Schwannoma
No
Lost to follow-up after 5 months verze 2013, 59 years Male Asymptomatic Right side Right nephrectomy 15-cm mass Intraparenchymal upper pole Melanotic Schwannoma No Alive (1 year) Alive (36-month)
R
Right nephrectomy
Schwannoma
No
Alive (24-month)
L L R
LRN Left nephrectomy Right nephrectomy
Schwannoma Schwannoma Ancient schwannoma
No No No
Alive (6-month) NR Alive (8-month)
Abdominal pain, nausea
L
Left nephrectomy
Schwannoma
No
Alive (4-month)
Asymptomatic
R
Right nephrectomy
Schwannoma
No
Alive (1 year)
NR
Intraparenchymal, pelvis 7-cm Mass Intraparenchymal 4.8-cm Lobulated mass Hilum 8.5-cm Myxomatous Intraparenchymal fibrous mass mid-lower pole 7-cm Encapsulated Hilum microcystic mass 15-cm mass Intraparenchymal upper pole Melanotic
Abbreviations: F ¼ female; L ¼ left; LRN ¼ aparoscopic radical nephrectomy; M ¼ male; R ¼ right.
Paolo Verze et al
Clinical Genitourinary Cancer February 2014
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Melanotic Schwannoma: A Case of Renal Origin Figure 3 Morphologic and Immunohistochemical Features of Melanotic Schwannoma. (A) In This Field, the Tumor was Fairly Cellular Showing Spindle Cells. (B) Epithelioid Cells With Smudged-Appearing Chromatin. (C) Pigmented Tumor Cells Mixed With Macrophages Engulfed With Melanic Pigment in a Loose Textured Pattern. (D) Neoplastic Cells Showed a Strong and Diffuse Immunoreactivity With S-100 Protein
completed using total body bone scintigraphy that revealed the presence of a mild spot of tracer deposition at the level of the left eighth rib. Successive X-ray stratigraphy showed a benign posttraumatic pattern at the level of this suspicious area. The patient did not have any features of neurofibromatosis type 1 or type 2. The only significant clinical alteration was a diffused hyperpigmentation of the trunk. Because of the large dimension of the renal mass, the patient was directly scheduled to undergo a right radical nephrectomy without the performance of a mass biopsy. The surgery was performed using an open transperitoneal approach through a median incision. The operative time was 135 minutes, and blood loss was 250 mL. The patient was discharged on day 7 after surgery and no perioperative or long-term complications were reported according to Clavien-Dindo grade. The kidney mass measured 15 12 cm and was surrounded by a fibrous capsule. On a cut section, a 15 12 cm well circumscribed mass compressing the renal parenchima was observed. The cut surface showed areas of hemorrhage and cystic degenerations (Fig. 2). At a 12-month follow-up CT scan the patient was free of recurrence.
Discussion
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-
Schwannomas are uncommon tumors that originate from the Schwann cell of the peripheral nerve sheath and are most common in the head and neck, extremities, and posterior mediastinum.1 Although 3% of schwannomas occur in the retroperitoneum, involvement of parenchimal organs is extremely uncommon. To our knowledge, Phillips and Baumrucker were the first to report a case of a neuronal tumor that was localized in the left renal hilum.2
Clinical Genitourinary Cancer February 2014
To date, we could find 27 cases of renal schwannoma that have been reported in medical literature taking into consideration publications in English and other languages. Table 1 summarizes data regarding these cases including the present case. The average age was 52 years (range, 18-84 years); male-to-female ratio was 1:1.6; average tumor size was 8.47 cm (range, 2-28 cm). The most frequent localization was on the right side rather than the left side (19 tumors vs. 7, respectively). Moreover, considering the organ distribution of the tumors, the most frequent localizations were ileopelvic and intraparenchymal. In 5 cases, malignant changes were found (19.2%). Out of the reported 27 cases, 19 were symptomatic with flank pain and generalized malaise with weight loss being the most frequently reported symptoms. We performed a Student t test and c2 test to determine if symptomatic patients presented larger tumor size or specific localization. Statistical analysis showed no difference between symptomatic and asymptomatic patients based on tumor size (P ¼ .27) or tumor localization (P ¼ .79). It is worthy to note that most of the tumors arose from the hilar region of the kidney because of the major nerve tissue density at this level. Despite the fact that schwannoma normally behave in a benign fashion, it could be important to recognize an eventual malignant pattern because of the clinical consequences in terms of disease-free survival and general prognosis. At this time there are no clear clinical or radiological indications that can help in differentiating between a benign or malignant lesion. Melanotic schwannoma (MS) is a rare, distinctive, potentially malignant neoplasm often diagnosed incidentally during pathologic examination. MSs are of neural crest origin, probably caused by the
Paolo Verze et al neoplastic proliferation of a common precursor cell for Schwann cells and melanocytes. More than 53% of MS cases involve cranial or spinal nerve roots; rarer examples are located in the gastrointestinal tract, skin, soft tissue, bone, heart, and bronchus.19-23 To the best of our knowledge, no other cases of renal MS have been reported in the literature. Compared with previously reported cases, there were no specific radiological or clinical features suggesting the presence of a melanotic histotype, and exact diagnosis can be exclusively confirmed using histological assessment. Rare cases of MS affecting a parenchimal organ have been described (2 cases localized in the lung21,24 and 1 in the pancreas).25 Microscopically, the tumor was composed mainly of spindle cells with a loose textured pattern and with microcystic formation, and some cellular areas composed of spindle and epithelioid cells with smudged-appearing chromatin (Fig. 3A and B). Strikingly, numerous pigmented tumor cells were seen, mixed with macrophages engulfed with melanic pigment (melanophages) (Fig. 3C). Cytoplasmic intranuclear vacuoles were seen in the tumor cells, some of which contained melanic pigment. Vascular sclerosis and hemorrhage were observed. Necrosis and mitoses were not observed. The tumor cells showed strong and diffuse immunoreactivity for S100 protein (Fig. 3D), and strong immunoreactivity for glial fibrillary acid protein in cellular areas were seen. CD34 was expressed only in the endothelial cells. Keratins, epithelial membrane antigen, human melanoma black, and melanoma antigen recongnized by T-cell1 were negative in the tumor cells, however the latter 2 antibodies highlighted the numerous melanophages. The differential diagnosis includes renal cell carcinoma (RCC) and, in particular, the recently described translocation renal cell carcinoma,19,24 low-grade malignant peripheral nerve sheath tumor, renal PEComa, sarcomatoid carcinoma, and melanoma. Distinguishing PEComa, and t(6;11) RCCs might be difficult, because both tumors label for melanocytic markers, ie, human melanoma black and melan A, however, not for S-100 protein. The main differential diagnosis is with the melanoma. Melanocytic immunohistochemical markers are not useful in this distinction, because they are frequently expressed in both tumor categories. However, malignant melanoma does not show adipose-like cells of MS, and usually melanoma cells show pleomorphic nuclei with prominent, and eosinophilic nucleoli; moreover, the identification of pericellular basement membrane using histochemical (reticulin) and immunohistochemical (collagen IV) stains or electron microscopy is more specific for MS.
Conclusion Renal schwannomas are very rare tumors that usually behave in a benign fashion. MS is a rare variant of schwannoma composed
of melanin-producing cells and its renal location is exceedingly rare. To our knowledge, this is the first report of a case of MS of renal origin.
Disclosure The authors have stated that they have no conflicts of interest.
References 1. Hung SF, Chung SD, Lai MK, et al. Renal schawannoma: case report and literature review. Urology 2008; 72:716.e3-6. 2. Phillips CA, Baumrucker G. Neurilemmoma (arising in the hilus of left kidney). J Urol 1955; 73:671-3. 3. KUZ’MINA VE. [Neurinoma of the kidney capsule]. Urol Mosc 1962 Jul-Aug; 27: 52-3, Russian. No abstract available. 4. Fein RL, Hamm FC. Malignant schwannoma of the renal pelvis: a review of the literature and a case report. J Urol 1965 Oct; 94(4):356-61. 5. Bair ED, Woodside JR, Williams WL, Borden TA. Perirenal malignant Schwannoma presenting as renal cell carcinoma. Urology 1978 May; 11(5):510-2. 6. Steers WD, Hodge GB, Johnson DE, Chaitin BA, Charnsangavej C. Benign retroperitoneal neurilemoma without von Recklinghausen’s disease: a rare occurrence. J Urol 1985 May; 133(5):846-8. 7. Somers WJ, Terpenning B, Lowe FC, Romas NA. Renal parenchymal neurilemoma: a rare and unusual kidney tumor. J Urol 1988 Jan; 139(1):109-10. 8. Kitagawa K, Yamahana T, Hirano S, Kawaguchi S, Mikawa I, Masuda S, Kadoya M. MR imaging of neurilemoma arising from the renal hilus. J Comput Assist Tomogr 1990 Sep-Oct; 14(5):830-2. 9. Ma KF, Tse CH, Tsui MS. Neurilemmoma of kidneyea rare occurrence. Histopathology 1990 Oct; 17(4):378-80. 10. Naslund MJ, Dement S, Marshall FF. Malignant renal schwannoma. Urology 1991 Nov; 38(5):477-9. 11. Romics I, Bach D, Beutler W. Malignant schwannoma of kidney capsule. Urology 1992 Nov; 40(5):453-5. 12. Ikeda I, Miura T, Kondo I, Kameda Y. Neurilemmoma of the kidney. Br J Urol 1996 Sep; 78(3):469-70. 13. Singer AJ, Anders KH. Neurilemoma of the kidney. Urology 1996 Apr; 47(4): 575-81, Review. 14. Pantuck AJ, Barone JG, Amenta PS, Smilow PC, Cummings KB. Diagnosis and management of malignant perirenal schwannoma. Am Surg 1996 Dec; 62(12): 1024-7. 15. Alvarado-Cabrero I, Folpe AL, Srigley JR, Gaudin P, Philip AT, Reuter VE, Amin MB. Intrarenal schwannoma: a report of four cases including three cellular variants. Mod Pathol 2000 Aug; 13(8):851-6. 16. Tsurusaki M, Mimura F, Yasui N, Minayoshi K, Sugimura K. Neurilemoma of the renal capsule: MR imaging and pathologic correlation. Eur Radiol 2001; 11(9): 1834-7. 17. Cachay M, Sousa-Escandón A, Gibernau R, Benet JM, Valcacel JP. Malignant metastatic perirenal schwannoma. Scand J Urol Nephrol 2003; 37(5):443-5. 18. Singh V, Kapoor R. A typical presentations of benign retroperitoneal schwannoma: report of three cases with review of literature. Int Urol Nephrol 2005; 37(3):547-9. 19. Gobbo S, Eble JN, Huang J, et al. Schwannoma of the kidney. Mod Pathol 2008; 21:779-83. 20. Chetty R, Vajpeyi R, Pennick JL. Psammomatous melanotic schwannoma presenting as colonic polyps. Virchows Arch 2007; 451:717-20. 21. Lin YF, His SC, Chang JL, et al. Intrapulmonary psammomatous melanotic schwannoma. J Thorac Cardiovasc Surg 2009; 137:e25-7. 22. Kachler KC, Russo PA, Katenkanp D. Melanocitic schwannoma of the cutaneous and subcutaneous tissue: three cases and a review of the literature. Melanoma Res 2008; 18:438-42. 23. Burns DK, Silva FG, Forde KA, et al. Primary melanocytic schwannoma of the stomach. Evidence of dual melanocytic and schwannian differentiation in an extraaxial site in a patient without neurofibromatosis. Cancer 1983; 52:1432-41. 24. Simansky DA, Aviel-Ronen S, Reder I, et al. Psammomatous melanotic schwannoma: presentation of a rare primary lung tumor. Ann Thorac Surg 2000; 70:671-2. 25. Akiyoshi T, Ueda Y, Yanai K, et al. Melanotic schwannoma of the pancreas: report of a case. Surg Today 2004; 34:550-3.
Clinical Genitourinary Cancer February 2014
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Melanotic Schwannoma: A Case of Renal Origin Paolo Verze,1 Anna Somma,2 Ciro Imbimbo,1 Gelsomina Mansueto,2 Vincenzo Mirone,1 Luigi Insabato2 Clinical Practice Points Schwannomas are uncommon tumors that originate
Melanotic schwannoma is a rare variant probably
from the Schwann cells of the peripheral nerve sheath and are exceedingly rare in the kidneys. We report on a case of an incidental large renal tumor which was diagnosed as melanotic schwannoma. To the best of our knowledge this is the first case of renal origin reported.
caused by the neoplastic proliferation of a common precursor cell for Schwann cells and melanocytes and can develop a potentially malignant clinical behavior.
Clinical Genitourinary Cancer, Vol. 12, No. 1, e37-41 ª 2014 Elsevier Inc. All rights reserved. Keywords: Kidney tumor, Melanotic, Rare variant, Renal mass, Schwannoma
Case Report A 59-year-old man, otherwise healthy, was discovered to be affected with a large mass of the right kidney during an occasional 1 Department of Neurosciences, Sciences of Reproduction and Odontostomatology, Urology Unit 2 Department of Biomorphological and Functional Science, Anatomic Pathology Unit, University of Naples “Federico II,” Naples, Italy
Submitted: Jul 5, 2013; Revised: Sep 6, 2013; Accepted: Sep 24, 2013; Epub: Sep 28, 2013 Address for correspondence: Paolo Verze, MD, PhD, Via Sergio Pansini, 5, 80131 Naples, Italy Fax þ39-0817464311; e-mail contact: [email protected]
Figure 1 Computed Tomography Scan Showed a Tumor Localized at Upper Pole of the Kidney With Concomitant Downward Displacement of Renal Hilum
1558-7673/$ - see frontmatter ª 2014 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.clgc.2013.09.005
abdominal ultrasound while undergoing a spontaneous health checkup visit. He had no urologic symptoms. A multiphase computed tomography (CT) scan using a GE 64-slice multi detector computed tomography was performed. The CT scan revealed a 12 10 cm renal tumor located at the upper pole of the kidney with concomitant downward displacement of the renal hilum. After contrast injection, during the arterial phase the mass showed a contrast enhancement directly supplied through an additional polar branch of the renal artery. Furthermore, large central necrotic areas were detected (Fig. 1). Despite its large size, the mass was not compressing the ureter and not cause hydronephrosis. The workup was within normal limits. Preoperative tumor stage assessment was
Figure 2 The Cut Surface of the Renal Mass Showed Areas of Hemorrhage, and Cystic Change
Clinical Genitourinary Cancer February 2014
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Investigator
Year
Age, Years
Sex
Side
Treatment
Size (cm) / Gross
Location
Diagnosis
Malignancy
Patient Status (Follow-Up)
Phillips2
1955
56
M
L
Left nephrectomy
12-cm Encapsulated tumor
Pelvis
Schwannoma
No
NR
Kuz’mina3
1962
33
F
R
Right nephrectomy
Encapsulated rubbery, pale gray tumor
Capsule
Schwannoma
No
NR
Fein4
1965
51
F
R
Right nephrectomy
6-cm Well encapsulated mass
Pelvis
Schwannoma
No
Alive (24-month)
Bair5
1978
56
M
R
Right nephrectomy
7-cm Mass
Hilum
Schwannoma
No
Alive (5-month)
Steers6
1985
50
F
R
Tumorectomy
9-cm multicystic mass
Hilum
Schwannoma
No
Somers7
1988
55
F
L
Left nephrectomy
No
L
Left nephrectomy
Intraparenchymal upper pole Hilum
Schwannoma
Upper abdominal pain and high fever
Cellular schwannoma
NR
NR
M
Epigastric pain
R
Right nephrectomy
No
Alive (1-year)
F
L
Left nephrectomy
Malignant schwannoma
Yes
Died after 15 months
1992
52
M
R
Right nephrectomy
Large infiltrating mass
Capsule
Malignant schwannoma
Yes
Died after 3 months
Ikeda12 Singer13
1996 1996
89 70
M F
Anemia, mild abdominal discomfort, weight loss Back and flank pain, fever, anemia Abdominal pain Asymptomatic
Intraparenchymal and pelvis Intraparenchymal upper pole
Cellular schwannoma
50
5.1-cm Well defined solid lobular mass 2.8-cm Well demarcated yellowish tumor 8-cm Well encapsulate yellowish tumor 14-cm Mass
Kitagawa8
1990
51
M
Ma9
1990
67
Naslund10
1991
Romics11
R L
Right nephrectomy Left nephrectomy
Pelvis Hilum
Schwannoma Schwannoma
No No
NR Alive (18-month)
Pantuck14 AlvaradoCabrero15 AlvaradoCabrero15 AlvaradoCabrero15
1996 2000
50 18
F F
Palpable mass Flank pain
R R
Right nephrectomy Right nephrectomy
NR 6-cm Well demarcated mass 28-cm Mass 6.2-cm Mass
Perirenal Intraparenchymal
Malignant schwannoma Schwannoma
Yes No
Died after 42 months Alive (42-month)
2000
84
M
Incidental finding
R
Right nephrectomy
4-cm Mass
Intraparenchymal
Cellular schwannoma
No
Alive (54-month)
2000
40
F
L
Left Nephrectomy
12.5-cm Mass
Intraparenchymal
Cellular schwannoma
No
Alive (12-month)
AlvaradoCabrero15
2000
45
M
Flank pain, fever, abdominal mass, anemia Flank and abdominal pain
L
Left Nephrectomy
16-cm Mass
Intraparenchymal
Ancient schwannoma
No
Alive (60-month)
Symptoms Generalized malaise, weight loss, fever, flank pain, mild anemia Generalized malaise, weight loss, mild fever, flank mass Recurrent pyelonephritis, palpable mass, pyuria Hypertension, microhematuria Microhematuria, palpable mass Incidental findings
NR Alive (18-month)
Melanotic Schwannoma: A Case of Renal Origin
Clinical Genitourinary Cancer February 2014
Table 1 Summary of Data From All Reported Cases
Table 1 Continued Investigator
Year
Age, Years
Sex
Tsurusaky16
2001
69
F
Incidental finding
L
Tumorectomy
Cachay17
2003
74
F
Asymptomatic
R
Singh18
2005
40
M
Singh18
2005
35
M
Hung1 Gobbo19 Gobbo19
2007 2008 2008
36 59 27
F F F
Renal colicky pain, vomiting Flank pain, gross hematuria Palpable mass, flank pain Asymptomatic Incidental finding
Gobbo19
2008
35
F
Verze (present case)
2013
59
M
Symptoms
Side
Treatment
Size (cm) / Gross
Location
Diagnosis
Malignancy
Patient Status (Follow-Up) NR
Capsule
Schwannoma
No
Right nephrectomy
White mass with necrosis 9-cm Mass
Perirenal
Malignant schwannoma
Yes
L
Left nephrectomy
3-cm Firm mass
Hilum
Schwannoma
No
Lost to follow-up after 5 months verze 2013, 59 years Male Asymptomatic Right side Right nephrectomy 15-cm mass Intraparenchymal upper pole Melanotic Schwannoma No Alive (1 year) Alive (36-month)
R
Right nephrectomy
Schwannoma
No
Alive (24-month)
L L R
LRN Left nephrectomy Right nephrectomy
Schwannoma Schwannoma Ancient schwannoma
No No No
Alive (6-month) NR Alive (8-month)
Abdominal pain, nausea
L
Left nephrectomy
Schwannoma
No
Alive (4-month)
Asymptomatic
R
Right nephrectomy
Schwannoma
No
Alive (1 year)
NR
Intraparenchymal, pelvis 7-cm Mass Intraparenchymal 4.8-cm Lobulated mass Hilum 8.5-cm Myxomatous Intraparenchymal fibrous mass mid-lower pole 7-cm Encapsulated Hilum microcystic mass 15-cm mass Intraparenchymal upper pole Melanotic
Abbreviations: F ¼ female; L ¼ left; LRN ¼ aparoscopic radical nephrectomy; M ¼ male; R ¼ right.
Paolo Verze et al
Clinical Genitourinary Cancer February 2014
- e39
Melanotic Schwannoma: A Case of Renal Origin Figure 3 Morphologic and Immunohistochemical Features of Melanotic Schwannoma. (A) In This Field, the Tumor was Fairly Cellular Showing Spindle Cells. (B) Epithelioid Cells With Smudged-Appearing Chromatin. (C) Pigmented Tumor Cells Mixed With Macrophages Engulfed With Melanic Pigment in a Loose Textured Pattern. (D) Neoplastic Cells Showed a Strong and Diffuse Immunoreactivity With S-100 Protein
completed using total body bone scintigraphy that revealed the presence of a mild spot of tracer deposition at the level of the left eighth rib. Successive X-ray stratigraphy showed a benign posttraumatic pattern at the level of this suspicious area. The patient did not have any features of neurofibromatosis type 1 or type 2. The only significant clinical alteration was a diffused hyperpigmentation of the trunk. Because of the large dimension of the renal mass, the patient was directly scheduled to undergo a right radical nephrectomy without the performance of a mass biopsy. The surgery was performed using an open transperitoneal approach through a median incision. The operative time was 135 minutes, and blood loss was 250 mL. The patient was discharged on day 7 after surgery and no perioperative or long-term complications were reported according to Clavien-Dindo grade. The kidney mass measured 15 12 cm and was surrounded by a fibrous capsule. On a cut section, a 15 12 cm well circumscribed mass compressing the renal parenchima was observed. The cut surface showed areas of hemorrhage and cystic degenerations (Fig. 2). At a 12-month follow-up CT scan the patient was free of recurrence.
Discussion
e40
-
Schwannomas are uncommon tumors that originate from the Schwann cell of the peripheral nerve sheath and are most common in the head and neck, extremities, and posterior mediastinum.1 Although 3% of schwannomas occur in the retroperitoneum, involvement of parenchimal organs is extremely uncommon. To our knowledge, Phillips and Baumrucker were the first to report a case of a neuronal tumor that was localized in the left renal hilum.2
Clinical Genitourinary Cancer February 2014
To date, we could find 27 cases of renal schwannoma that have been reported in medical literature taking into consideration publications in English and other languages. Table 1 summarizes data regarding these cases including the present case. The average age was 52 years (range, 18-84 years); male-to-female ratio was 1:1.6; average tumor size was 8.47 cm (range, 2-28 cm). The most frequent localization was on the right side rather than the left side (19 tumors vs. 7, respectively). Moreover, considering the organ distribution of the tumors, the most frequent localizations were ileopelvic and intraparenchymal. In 5 cases, malignant changes were found (19.2%). Out of the reported 27 cases, 19 were symptomatic with flank pain and generalized malaise with weight loss being the most frequently reported symptoms. We performed a Student t test and c2 test to determine if symptomatic patients presented larger tumor size or specific localization. Statistical analysis showed no difference between symptomatic and asymptomatic patients based on tumor size (P ¼ .27) or tumor localization (P ¼ .79). It is worthy to note that most of the tumors arose from the hilar region of the kidney because of the major nerve tissue density at this level. Despite the fact that schwannoma normally behave in a benign fashion, it could be important to recognize an eventual malignant pattern because of the clinical consequences in terms of disease-free survival and general prognosis. At this time there are no clear clinical or radiological indications that can help in differentiating between a benign or malignant lesion. Melanotic schwannoma (MS) is a rare, distinctive, potentially malignant neoplasm often diagnosed incidentally during pathologic examination. MSs are of neural crest origin, probably caused by the
Paolo Verze et al neoplastic proliferation of a common precursor cell for Schwann cells and melanocytes. More than 53% of MS cases involve cranial or spinal nerve roots; rarer examples are located in the gastrointestinal tract, skin, soft tissue, bone, heart, and bronchus.19-23 To the best of our knowledge, no other cases of renal MS have been reported in the literature. Compared with previously reported cases, there were no specific radiological or clinical features suggesting the presence of a melanotic histotype, and exact diagnosis can be exclusively confirmed using histological assessment. Rare cases of MS affecting a parenchimal organ have been described (2 cases localized in the lung21,24 and 1 in the pancreas).25 Microscopically, the tumor was composed mainly of spindle cells with a loose textured pattern and with microcystic formation, and some cellular areas composed of spindle and epithelioid cells with smudged-appearing chromatin (Fig. 3A and B). Strikingly, numerous pigmented tumor cells were seen, mixed with macrophages engulfed with melanic pigment (melanophages) (Fig. 3C). Cytoplasmic intranuclear vacuoles were seen in the tumor cells, some of which contained melanic pigment. Vascular sclerosis and hemorrhage were observed. Necrosis and mitoses were not observed. The tumor cells showed strong and diffuse immunoreactivity for S100 protein (Fig. 3D), and strong immunoreactivity for glial fibrillary acid protein in cellular areas were seen. CD34 was expressed only in the endothelial cells. Keratins, epithelial membrane antigen, human melanoma black, and melanoma antigen recongnized by T-cell1 were negative in the tumor cells, however the latter 2 antibodies highlighted the numerous melanophages. The differential diagnosis includes renal cell carcinoma (RCC) and, in particular, the recently described translocation renal cell carcinoma,19,24 low-grade malignant peripheral nerve sheath tumor, renal PEComa, sarcomatoid carcinoma, and melanoma. Distinguishing PEComa, and t(6;11) RCCs might be difficult, because both tumors label for melanocytic markers, ie, human melanoma black and melan A, however, not for S-100 protein. The main differential diagnosis is with the melanoma. Melanocytic immunohistochemical markers are not useful in this distinction, because they are frequently expressed in both tumor categories. However, malignant melanoma does not show adipose-like cells of MS, and usually melanoma cells show pleomorphic nuclei with prominent, and eosinophilic nucleoli; moreover, the identification of pericellular basement membrane using histochemical (reticulin) and immunohistochemical (collagen IV) stains or electron microscopy is more specific for MS.
Conclusion Renal schwannomas are very rare tumors that usually behave in a benign fashion. MS is a rare variant of schwannoma composed
of melanin-producing cells and its renal location is exceedingly rare. To our knowledge, this is the first report of a case of MS of renal origin.
Disclosure The authors have stated that they have no conflicts of interest.
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