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Year : 2014  |  Volume : 57  |  Issue : 2  |  Page : 298-300
Primary primitive neuroectodermal tumor of kidney: A rare case report with diagnostic challenge

Department of Pathology and Laboratory Science, Armed Forces Medical College, Command Hospital, Pune, Maharashtra, India

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Date of Web Publication19-Jun-2014


Primary primitive neuroectodermal tumors (PNETs) of the kidney are quite rare and can be mistaken for a wide variety of other small round blue cell tumors which includes rhabdomyosarcoma, Wilm's tumor, carcinoid, neuroblastoma, clear cell sarcoma of the kidney, lymphoma etc. Renal Ewings/PNET can occur in the age group from 4 to 61 years. Approximately, 90% of Ewing sarcoma (ES)/PNET have a specific t(11;22) which results in a chimeric EWS-FLI-1 fusion protein. Immunohistochemical for the carboxy-terminus of FLI-1 is sensitive and highly specific for the diagnosis of ES/PNET. Herein, we have an interesting presentation in a 23-year-old male who came with neck pain and progressive quadriparesis and was diagnosed as a case of poorly differentiated malignant tumor with a differential of lymphoma versus metastatic renal cell carcinoma. The patient's condition deteriorated fast and he had a rapid downhill course. The final diagnosis of Ewings/PNET was confirmed at autopsy.

Keywords: FLI-1, kidney, primitive neuroectodermal tumor

How to cite this article:
Kakkar S, Gupta D, Kaur G, Rana V. Primary primitive neuroectodermal tumor of kidney: A rare case report with diagnostic challenge. Indian J Pathol Microbiol 2014;57:298-300

How to cite this URL:
Kakkar S, Gupta D, Kaur G, Rana V. Primary primitive neuroectodermal tumor of kidney: A rare case report with diagnostic challenge. Indian J Pathol Microbiol [serial online] 2014 [cited 2023 Sep 26];57:298-300. Available from:

   Introduction Top

Ewings primitive neuroectodermal tumor (PNET) as a group has incidence of less than 1%. They arise from the primitive neuroectoderm and therefore have a propensity to arise from multiple sites. The most common reported sites being trunk, extremities, brain, spinal cord and sympathetic nervous system as well as peripheral tissues like the chest wall (Askin's tumor), paraspinal region and less commonly, the genitourinary tract. Renal primitive neuroectodermal tumor (rPNET) as a member of Ewing's sarcoma family is extremely rare. Extensive search on the internet yielded only isolated case reports however study on relatively large number of cases was published and includes 79 cases from the files of the National Wilms Tumor Study Grou. [1] Primary Ewing's sarcoma occurring in the kidney is a rare neoplastic disease of high malignant potential with a tendency toward early metastases. The differential diagnosis is usually broad with frequent overlapping features between the entities.

The presentation of these is usually variable not specific and can range from flank pain, hematuria and symptoms due to distant metastasis which is more commonly seen. The prognosis is very poor with a median survival of only about 2 years. [2]

We present here a case of Ewing's sarcoma/PNET occurring in a young adult with an unusual presentation.

   Case report Top

A 23-year-old male patient non-smoker was admitted with complaints of tingling sensation, numbness and weakness initially in the bilateral upper limbs which thereafter progressed to involve both lower limbs. There was history of neck pain of 1 1/2 month duration localized to the lower cervical region. No history of preceding trauma was present. On general physical examination, patient was found to be well oriented and conscious. His vitals were within normal limits. Systemic examination revealed increased tone in all four limbs with a power of 0/5. There was decreased fine touch and temperature sensation below C3 with urinary incontinence. The magnetic resonance imaging showed a retroperitoneal mass with C2-C3 metastasis with prevertebral and anterior epidural component enhancing on contrast. The contrast-enhanced computed tomography showed similar findings of a retroperitoneal lobulated mass with eccentric fluid intensities with left renal vein and left inferior vena cava (IVC) involvement [Figure 1]. Viewing the patients clinical and radiological profile, an urgent C3 corpectomy with cage fixation and anterior plating was done on 2 nd day and the patient was placed on mechanical ventilation. Based on the clinical profile, the imaging findings and the presence of metastasis, non-Hodgkins lymphoma verses renal cell carcinoma was considered in the differential diagnosis.

Tissue from the corpectomy was submitted for histopathology which showed chiefly necrotic tissue with highly atypical cells based on which a provisional diagnosis of metastasis from a poorly differentiated tumor was rendered.

Fine-needle aspiration cytology was simultaneously done from the retroperitoneal mass which was reported as poorly differentiated malignant carcinoma with neuroendocrine differentiation. During the course of his stay in the intensive care unit, patient developed deranged biochemical parameters with superadded bronchopneumonia. A Tru-cut biopsy of the retroperitoneal mass was performed. He had a downhill course and succumbed to his illness 2 weeks after admission.

At autopsy there was a large heterogenous retroperitoneal mass measuring 19 cm × 17 cm × 13 cm and weighing 1.5 kg arising from the left kidney which was completely obliterating it and also involving the left renal vein and IVC [Figure 2]a]. Grossly the mass was greyish brown with areas of hemorrhage and necrosis [Figure 2]b]. The left adrenal was grossly uninvolved. The lungs on serial sectioning showed multiple 1-1.5 cm yellowish white nodules. The liver, spleen, pancreas and large and small intestine appeared grossly uninvolved.
Figure 1: Contrast-enhanced computed tomography chest and abdomen showing heterogeneously (17 cm × 14 cm × 15 cm) enhancing mass lesion likely of renal origin with extension into left renal vein and inferior vena cava associated with peritumoral and retroperitoneal lymph nodes

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Figure 2: (a) In situ tumor mass which is yellowish brown in color and has a lobulated appearance. (b) Cut surface of tumor having a variegated appearance with areas of necrosis and a tumor thrombus entering the inferior vena cava as demonstrated by the probe

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Histological examination of the Tru-cut biopsy and post mortem kidney mass showed tumor cells arranged in solid sheets, cords and trabeculae infiltrating the renal parenchyma. The tumor was composed of small round blue cells with scant cytoplasm, uniform nuclei and stippled chromatin [Figure 3]a]. Large necrotic areas were seen interspersed between the tumor cells. Mitosis was 3-4/hpf. Similar nests of tumor tissue were seen infiltrating the lung parenchyma as well as the pancreas. A panel of immunohistochemical (IHC) markers were placed which showed tumor cells to be positive for CD99 and FLI-1 [Figure 3]b and c] and negative for cytokeratin (CK), leukocyte common antigen (LCA), vimentin, desmin, synaptophysin, chromogranin, neuron-specific enolase and terminal deoxynucleotidyl transferase (TdT). Based on the histomorphology and IHC findings a diagnosis of primary Ewings/PNET of the kidney was offered with metastasis to the lung, bone and pancreas.
Figure 3: (a) H and E, section (magnification ×20) shows a monotonous population of small, round blue cells with scant cytoplasm, uniform nuclei and stippled chromatin infiltrating through the renal parenchyma. (b) Immunohistochemical stain for CD99 shows membranous positivity of these tumor cells. (c) FLI-1 nuclear
immunostaining in the tumor cells

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   Discussion Top

PNET of the kidney is a rare entity. The age range varies between 4 and 61 years with majority in the second and third decades of life.

The male to female ratio is about 3:1. The presenting symptoms and clinical signs are non-specific and similar to those of other renal tumors. However ours was a rather unusual case were the patient presented with quadriparasis. Of all reported metastatic cases, 44% present with lung metastases only and 51% have a bone or bone marrow involvement with or without lung metastases and 5% present with metastases in other organs. [3]

The largest series of rPNET is a series from India published by Thyavihally et al. This series included 16 patients who were treated in Tata Memorial Hospital. [4] However, the first report came in the year 1994 when Mor et al. described a characteristic primary renal neoplasia consistent with the diagnosis of malignant peripheral PNET. [5]

The origin of this tumor is though debatable but studies show that it is derived from cells that have migrated from the neural tube with variable capability of ectodermal or neuronal differentiation and these tumors can arise anywhere from the brain to the sacrum. The few cases that have been reported reveal a variable presentation and an aggressive behavior. The distinction from other primary malignancies of the kidney is crucial for prognosis. The differential diagnosis includes extraosseous Ewing's sarcoma, rhabdomyosarcoma, Wilm's tumor, carcinoid, neuroblastoma, clear cell sarcoma of the kidney, lymphoma, the small cell variant of osteosarcoma, desmoplastic small round cell tumor and nephroblastoma. [6]

Jimenez et al. [7] published clinicopathologic and IHC analysis of 11 cases of Primary Ewing's sarcoma/PNET of the kidney and mentioned a mean age of 18-49 years and mean follow-up of 28 months (range: 6-64 months) which showed 4 lung and pleural metastases, one bone metastases, two local recurrences and five deaths from disease (median time to death 16.8 months). In our case, the patient was a young 23-year-old male who had presented to our hospital with quadriparesis and succumbed to his illness within a short period of 2 weeks. The post mortem findings were suggestive of metastasis to lung, bone and pancreas.

Histologically Ewing sarcoma/PNET is composed by monomorphic small round cells which form Homer Wright rosettes. We did not see rosettes on histology in our case. Immunohistochemically the tumor cells are strongly positive for CD99 and (FLI)-1.

In our case, the presence of MIC-2 gene products known also as CD99 on IHC suggested the diagnosis of PNET. This was further confirmed by doing FLI-1/EWS by IHC which validated our diagnosis. The reactivity to CK, vimentin, desmin, myogenin, LCA, synaptophysin and TdT as expected was negative.

Cytogenetic studies (not performed in our case) can also be used to demonstrate the association of PNET and Ewing's sarcoma with translocation of the long arms of chromosome 11 and 22, t(11;22)(q22;q12). [8],[9] Despite their genetic and antigenic similarity many authors currently recognize PNET and extra-skeletal Ewing's sarcoma of the kidney as separate entities.

Some rPNET and malignant rhabdomysarcoma (embryonal/alveolar rhabdomyosarcoma) of kidney and renal rhabdoid tumor (paediatric tumors) may show histological similarity (mimicking) but, clinical presentation, IHC stains, molecular cytogenetic study and electron microscopy can very well differentiate the rPNET with rhabdoid features, malignant rhabdomysarcoma (embryonal/alveolar rhabdomysarcoma) and rhabdoid tumor of kidney as separate entities. Weeks et al. reported eight cases suggestive for PNET but mimicking malignant rhabdomyosarcoma tumor. Although renal PNET and malignant rhabdomyosarcoma tumor show similar clinico-pathological features the later usually occurs in very young children. [10]

Two decades back there was lack of consensus on the criterion of diagnosis of rPNET with rhabdoid features, phenotypic malignant rhabdomyosarcoma and malignant rhabdoid tumor in extra-skeletal locations leading to difficulty in proper classification, but now the IHC staining, molecular cytogenetic and electron microscopic findings have helped to classify these as separate entities, but still there is overlapping in a small percentage of cases.

   Conclusion Top

rPNET is a rare tumor with aggressive clinical behavior and grave prognosis. These tumors can have a broad spectrum of presentation and the diagnosis of PNET should be considered in young adults presenting with renal mass.

   References Top

1.Parham DM, Roloson GJ, Feely M, Green DM, Bridge JA, Beckwith JB. Primary malignant neuroepithelial tumors of the kidney: A clinicopathologic analysis of 146 adult and pediatric cases from the National Wilms' Tumor Study Group Pathology Center. Am J Surg Pathol 2001;25:133-46.  Back to cited text no. 1
2.Casella R, Moch H, Rochlitz C, Meier V, Seifert B, Mihatsch MJ, et al. Metastatic primitive neuroectodermal tumor of the kidney in adults. Eur Urol 2001;39:613-7.  Back to cited text no. 2
3.Cotterill SJ, Ahrens S, Paulussen M, Jürgens HF, Voûte PA, Gadner H, et al. Prognostic factors in Ewing's tumor of bone: Analysis of 975 patients from the European Intergroup Cooperative Ewing's Sarcoma Study Group. J Clin Oncol 2000;18:3108-14.  Back to cited text no. 3
4.Thyavihally YB, Tongaonkar HB, Gupta S, Kurkure PA, Amare P, Muckaden MA, et al. Primitive neuroectodermal tumor of the kidney: A single institute series of 16 patients. Urology 2008;71:292-6.  Back to cited text no. 4
5.Mor Y, Nass D, Raviv G, Neumann Y, Nativ O, Goldwasser B. Malignant peripheral primitive neuroectodermal tumor (PNET) of the kidney. Med Pediatr Oncol 1994;23:437-40.  Back to cited text no. 5
6.Gonlusen G, Ergin M, Paydas S, Bolat FA. Primitive neuroectodermal tumor of the kidney: A rare entity. Int Urol Nephrol 2001;33:449-51.  Back to cited text no. 6
7.Jimenez RE, Folpe AL, Lapham RL, Ro JY, O'Shea PA, Weiss SW, et al. Primary Ewing's sarcoma/primitive neuroectodermal tumor of the kidney: A clinicopathologic and immunohistochemical analysis of 11 cases. Am J Surg Pathol 2002;26:320-7.  Back to cited text no. 7
8.Sandberg AA, Bridge JA. Updates on cytogenetics and molecular genetics of bone and soft tissue tumors: Ewing sarcoma and peripheral primitive neuroectodermal tumors. Cancer Genet Cytogenet 2000;123:1-26.  Back to cited text no. 8 Alava E, Gerald WL. Molecular biology of the Ewing's sarcoma/primitive neuroectodermal tumor family. J Clin Oncol 2000;18:204-13.  Back to cited text no. 9
10.Weeks DA, Beckwith JB, Mierau GW, Zuppan CW. Renal neoplasms mimicking rhabdoid tumor of kidney. A report from the National Wilms' Tumor Study Pathology Center. Am J Surg Pathol 1991;15:1042-54.  Back to cited text no. 10

Correspondence Address:
Devika Gupta
Department Of Pathology and Laboratory Science, Armed Forces Medical College, Command Hospital, Pune - 411 040, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0377-4929.134723

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  [Figure 1], [Figure 2], [Figure 3]

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