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| Ahead of print
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Primary intracranial Ewing’s sarcoma/peripheral primitive neuroectodermal tumor in pediatric age group: A comprehensive review of literature
Mohammad Elbaroody, Ahmed Abdullah
Department of Neurosurgery, Faculty of Medicine, Cairo University, Cairo, Egypt
| Date of Submission | 09-Oct-2021 |
| Date of Decision | 03-Feb-2022 |
| Date of Acceptance | 12-Mar-2022 |
| Date of Web Publication | 12-Jul-2022 |
Correspondence Address:
Mohammad Elbaroody,
Department of Neurosurgery, Faculty of Medicine, Cairo University, Cairo
Egypt
 Source of Support: None, Conflict of Interest: None DOI: 10.4103/jpn.JPN_198_21
 Abstract | | |
Background: Ewing’s sarcoma (ES) forms about 1% of pediatric malignancies, and primary intracranial ES is an extremely rare entity. Materials and Methods: We report a case of primary Ewing’s sarcoma/peripheral primitive neuroectodermal tumor (ES/pPNET) in the posterior temporal-occipital region with an extension down into posterior fossa managed by gross total resection (GTR), and the skull was reconstructed using a titanium mesh followed by chemotherapy and 28 sessions of radiotherapy. The child is doing well 2 years after surgery with no recurrence in the last imaging. We reviewed the literature for 74 pediatric ES/pPNET cases reported in the last quarter of the century, focussing on surgical treatment, adjuvant therapy, and reported outcomes. Results: Most patients (81.1%) did not develop neither recurrence nor metastasis during the follow-up, and 55 patients (74.3%) were alive and free of disease at the last follow-up, and 19 patients were dead (25.7%). The mean time of survival was 12.679 months (95% confidence interval: 9.632–15.725). Conclusion: Primary intracranial ES/pPNET is an extremely rare tumor in the pediatric age group. Maximum safe resection followed by chemotherapy and radiotherapy is the cornerstone for the best outcome. Follow-up is recommended for the detection of recurrence or metastasis.
Keywords: Ewing’s sarcoma, intracranial, neuroectodermal tumors, pediatric
| Introduction | |  |
Primitive neuroectodermal tumor (PNET) was reported for the first time in the cerebellum as an undifferentiated tumor that did not meet the criteria of medulloblastoma, neuroblastoma, ependymoblastoma, or pineal tumors.[1] PNET could originate centrally from the central or sympathetic nervous system (cPNET) or peripherally from bone or soft tissue (pPNET), and both are different in behavior and prognosis.[2],[3] Ewing’s sarcoma (ES) is a primary malignancy from bone and may extend to soft tissues.[4] ES family tumors formed by ES/pPNET have genetic translocation of t(11;22)(q24;q12) and MIC-2 antigen expression in common.[5] Intracranially, ES more frequently originates in the skull base and to a lesser extent in the vault.[6],[7],[8] ES/pPNET usually grows as extradural mass and rarely violates the dura; it typically reaches large sizes before diagnosed.[9] We report ES/pPNET in the left posterior temporal-occipital region with an extension down into the posterior fossa in a 3-year-old boy.
| Materials and Methods | | |
Case report
Clinical presentation
A 3-year-old boy presented to the general practitioner with swelling behind his left ear, based on his provisional diagnosis as an abscess, and a trial of drainage of this swelling with subsequent massive bleeding occurred; he packed the swelling and referred the child to our tertiary center. On admission, the boy was alert and vitally stable without neurological deficits.
Imaging
Magnetic resonance imaging (MRI) brain with contrast was done and showed a large intracranial extra-axial lesion in the left posterior temporal-occipital region extending into posterior fossa and eroding the bone with soft tissue extending beneath the skin; it showed diffuse enhancement in T1-weighted images and no edema around the lesion was noted, as shown in [Figure 1]A and [Figure 1]B. Digital subtraction angiography (DSA) showed tumor blush with feeding arteries from left middle meningeal, accessory meningeal, posterior auricular, and occipital arteries with subsequent embolization of those arteries. | Figure 1: A: Axial and B: coronal postcontrast T1 MRI scans illustrating a well-defined, heterogeneously enhancing extra-axial mass in the left posterior temporal-occipital region with extension down into posterior fossa. C: Axial postoperative postcontrast T1 MRI scan 2 years after resection and adjuvant therapy
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Treatment
One day following embolization, left retrosigmoid curvilinear incision was done, excision of the soft tissue and the destructed bone done, the tumor was completely extradural with strong adherence to it, GTR was achieved of both supratentorial and posterior fossa parts, the transverse sinus was intact, and then coagulation of the dura was done. Replacement of the destructed bone with reshaped titanium mesh is fixed with screws, and the postoperative course was uneventful, as shown in [Figure 2].  | Figure 2: Intraoperative look after gross total resection of the tumor before placement of the titanium mesh. Green arrows, posterior petrous bone; blue arrow, transverse sinus; black (*), dura over occipital lobe; black (#), dura over posterior fossa
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Pathology
Histological examination showed malignant round blue cells with scanty cytoplasm with hematoxylin and eosin, as shown in [Figure 3]. Staining for MIC-2 (CD99), S100, and FLI-1 was positive, and staining for Desmin, LCA, BCL 2, creatine kinase (CK), placental alkaline phosphatase, CD 34, and neuron-specific enolase was negative, had occasional rosette-like pattern, frequent mitosis was noted with high power field, and these features confirmed the diagnosis with ES/pPNET tumor. | Figure 3: Immunohistochemistry pathological examination of the specimen with hematoxylin and eosin shows malignant round small blue cell tumor
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Adjuvant therapy, follow-up, and outcome
Postoperatively, a Techninum Tc99 bone scan showed a free surveyed skeleton. MRI whole spine and computed tomography of the thorax and abdomen excluded distant metastasis. The child finished his chemotherapy followed by 28 sessions of radiotherapy and he was in good condition without neurological deficit till the last follow-up imaging, which showed neither recurrence nor residual cells 2 years postoperatively till June 2021, as shown in [Figure 1]C.
Literature review
We reviewed the literature for ES/pPNET cases that were reported in the pediatric age group ≤ 18 years over the last 24 years (1996–2020). Only cases reported in the English language were included, and reported cases that did not provide information regarding the resection, follow-up, or outcome were omitted. [Table 1] summarizes the clinical data of 74 cases of intracranial ES/pPNET reported in the literature. | Table 1: Clinical data of 74 cases of Ewing’s sarcoma/pPNET reported in literature in the pediatric age group ≤ 18 years
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Statistical analysis
Microsoft Excel 2013 was used for data entry, and the Statistical Package for Social Sciences (SPSS) version 22 (SPSS, Armonk, NY, USA: International Business Machines Corporation) was used for data analysis. Simple descriptive statistics (arithmetic mean and standard deviation) were used for summary of quantitative data and frequencies used for qualitative data. The Kaplan–Meier survival curve was used to estimate overall survival and progression-free survival. The log rank test was used to compare the Kaplan–Meier survival curves for chemotherapy, radiotherapy, and surgical procedures with regard to overall survival and progression-free survival. The level of significance was set at probability (P) value less than 0.05.
Ethical considerations
Patient confidentiality was maintained following the Declaration of Helsinki. Owing to its retrospective nature, neither ethical board approval nor patient consenting was required, as there were no specific interventions for the patients enlisted in our study.
| Results | | |
There were 44 males (59.5%) and 30 females (40.5%). The mean age was 9.8 years (0.4–18 years). The mean follow-up was 2.7 years, and the median of last follow-up was 1.8 years. GTR was achieved in 43 patients (58.1%), subtotal resection (STR was achieved in 26 patients [35.1%]), and one patient did not receive any form of surgical treatment. Most patients (81.1%) did not develop neither recurrence nor metastasis during the follow-up, and 55 patients (74.3%) were alive and free of disease at the last follow-up, and 19 patients were dead (25.7%). [Table 2] summarizes patient’s different treatment modalities and outcomes. The mean time of survival was 12.679 months (95% confidence interval: 9.632–15.725) [Figure 4]A.  | Figure 4: A: Statistical graph for the overall survival at the last follow-up. B: The cumulative probability of survival in patients who achieved gross total resection (GTR) or not, C: patients received radiotherapy or not, D: patients received chemotherapy or not
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| Discussion | | |
ES forms about 1% of all pediatric malignancies, extraosseous ES is uncommon, and primary intracranial ES is very rare.[23],[46] There are no specific radiological signs that can confirm the diagnosis preoperatively, and ES/pPNET can be misdiagnosed as meningioma or hemangiopericytoma, lymphoma, and neuroblastoma. Asano et al.[19] reported an infant misdiagnosed as neuroblastoma at 21 months and underwent GTR followed by chemotherapy and radiotherapy and they revisited the pathology and rediagnosed it as ES/pPNET tumor.
ES affects boys more than girls with a ratio of 1.6–1.8:1.[12],[49] In our review, intracranial ES/pPNET affected 44 boys (60%) and 30 girls (40%) with a clear male predominance (1.5: 1) even for the intracranial type.
In the intracranial ES, frontal and parietal convexities are relatively common and the skull base is rarely involved.[23],[49] In our review, the most common location was the frontal region which was involved in 22 cases (30%), and the temporal region is the second common (27%).
ES is an aggressive bony tumor that frequently presents in the second decade of life,[50] whereas ES/pPNET can appear even in the first year of life. Niwa et al.[13] reported a 3-month-old case, and Patibandla et al.[31] reported an 11-month-old case. In 74 reported cases in the pediatric age group, the mean age for ES/pPNET was 9.9 years (ranging from 3 months to 18 years). Metastasis from ES is not uncommon, whereas metastasis from intracranial ES is rarely encountered.[12] It may be discovered at the time of diagnosis,[51] 2 months,[42] 3 months,[46] 8 months,[44] 2 years,[46] and even 3 years after surgery.[38] Primitive monomorphic round cells with little cytoplasm, round nuclei, and inconspicuous nucleoli are histopathological traits usually found in ES/pPNET.[45] However, it can be challenging to confirm an ES diagnosis, and cytogenetics and a molecular biological marker play an important role. MIC-2 is a specific marker that is expressed in ES family tumors and can differentiate pPNET from cPNET which is not found in the later one.[22] CD 99 is a surface glycoprotein which is a product of the MIC-2 gene and found essentially in all cases of ES/pPNET tumors.[52] The FLI1 gene located in 11q24 involved in the genetic translocation t(11;22)(q24;q12) in 90–95% of ES cases detected by fluorescent in situ hybridization technique is pathognomonic.[32],[46] In our case, histological examination revealed the most likely criteria for the diagnosis of ES/pPNET based on +ve CD99 in the cell membrane and +ve FLI1 gene.
ES/pPNET tumors need multimodality treatment for best prognosis, and maximum surgical resection possible followed by chemotherapy and radiotherapy could give the best outcome[22],[53],[54]; however, a more aggressive surgical resection in these cases may have led to a limited quality of life, as a result of mutilation and loss of function of the vital structures.[41] The cornerstone of treatment is surgical resection of the tumor,[47] and GTR was achieved in 43 cases (58%). In our review, patients with GTR form most of the patients (33/55) who are free of disease at the last follow-up; however, there was no difference in the overall survival whether GTR was achieved or not (P-value = 0.438) [as shown in [Table 3]]. In young children, high-dose chemotherapy could be better followed by radiotherapy; however, radiotherapy after surgery before chemotherapy could be better in adults or old children.[55],[56],[57] In our review, four cases were reported who underwent GTR and received neither chemotherapy nor radiation therapy[17],[19],[32] and still free of disease at the last follow-up. Neither chemotherapy nor radiotherapy had statistical significant difference regarding overall survival at the last follow-up (P-value = 0.113 and 0.068, respectively) [Figure 4]C and [Figure 4]D. Although the follow-up of patients who were free of disease and received chemotherapy alone, radiotherapy alone, or did not receive anything seems much longer than those who received the typical adjuvant treatment, we cannot take this as a rule because they are limited by their small numbers; this means that maximum safe GTR followed by chemotherapy and radiotherapy should be the standard for treatment. Our case had achieved GTR followed by chemotherapy and 28 sessions of radiotherapy and he was neurologically free without recurrence in the last imaging 2 years after surgery. Two years of follow-up is comparable to what is mentioned in the literature; however, metastasis still can occur later.[38],[46[Table 4] summarizes patients’ data by their last clinical status. The worst prognostic factor of ES/pPNET was the presence of metastatic disease at the time of diagnosis.[58] It seems that most children with intracranial ES/pPNET could be free of disease and the prognosis was not dismal as expected. As shown in [Table 4], 74% (55 cases) were alive and free of disease at the last follow-up: 23 cases of GTR and 18 cases of STR followed by chemotherapy and radiation therapy form the main bulk of surviving children. These data dictate that maximum safe resection whenever possible followed by chemotherapy and radiation therapy should be the standard, although there are rare cases in which this was not done, and they were free of disease at the last follow-up. In our review, the mortality forms about 26% of the whole cases (19 children): nearly 50% (10 cases) underwent GTR and 8 cases underwent STR. Although it seems that GTR did not differ from STR regarding mortality, only 2 out of 19 cases died after GTR was given, the typical protocol of chemotherapy and radiation therapy, this should support the standard treatment method. So, the main strategy for treatment is to prolong the survival through maximum safe surgical excision followed by adjuvant therapy, although this will not guarantee the survival, and this will give the best chance for the patients.  | Table 4: Summary of patient’s data by different treatment modalities and outcomes at last follow-up
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| Conclusion | | |
Primary intracranial ES/pPNET is an extremely rare tumor in the pediatric age group, which can be easily mistaken for other tumors. Maximum safe surgical excision followed by chemotherapy and radiotherapy gives the chance for the best prognosis of the patient and it is the standard care given to children. Follow-up is recommended for surveillance of recurrence or metastasis which may be delayed.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4]
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