A Rare Case of Primary Intracranial Ewing's Sarcoma

Sir, Extraosseous Ewing's sarcoma (EES), a rare tumor, comes under the ambit of the peripheral primitive neuroectodermal tumor/Ewing's sarcoma (pPNET/ES) family of round cell neuroectodermal origin tumors with a predilection for soft tissues of lower extremities, paravertebral, and retroperitoneal space.[1] A 32-month-old girl child presented with headache and projectile vomiting and decreased feeding for two months. Contrast enhanced-MRI brain revealed a 6.5 cm × 5.8 cm × 5.6 cm space-occupying lesion in the right temporal region [Figure 1]. She underwent right frontotemporal craniotomy with near total excision. Histopathological examination revealed a malignant small round blue cell tumor with cells having scanty cytoplasm, indistinct nucleoli, and nuclear molding, which were arranged in sheets with primitive rosette formation. Immunohistochemistry were positive for panCK, EMA, CD99, and Vimentin and was negative for WT-1, NKX2.2, TLE1, GFAP, EBP50, OLIG2, LIN28, and LCAM1. Integrase interactor (INI) expression was retained by the tumor and the MIB-1 labeling index was 45–50%. Fluorescent in situ hybridization (FISH) was positive for Ewing's sarcoma (EWS) rearrangement [Figure 2]. Positron emission tomography–computed tomography scan did not reveal systemic dissemination. She received craniospinal irradiation 36 Gy in 20 fractions over 4 weeks to the entire neuro-axis followed by boost to tumor bed till 56 Gy by volumetric modulated arc therapy technique by 6 MV photons followed by adjuvant chemotherapy with alternating weekly cycles of vincristine, adriamycin, cyclophosphamide, and ifosfamide and etoposide for 15 cycles each. The patient tolerated treatment well with only grade 2 vomiting, anemia, and thrombocytopenia. After one year of completion of treatment, the patient is disease-free and on regular follow-up.Figure 1: MRI showing mass lesion with intense heterogenous hyperintense enhancement in right temporal lobe. (a) Axial section of T1 non contrast image showing a mostly hypointense SOL in the right temporal region; (b) T1 Post contrast enhanced image showing intense heterogenous hyperintense enhancement in the right temporal SOL; (c) T2 weighted image showing solid cystic lesion in the right temporal region with hyperintense solid components and mass effect with considerable midline shift (d) FLAIR images showing solid cystic lesion with perilesional edema, mass effect and midline shift; (e) 95% dose distribution to the CSI plan- sagittal sectionsFigure 2: (a) H and E (400×) shows malignant small round blue cell tumor, cells with scant cytoplasm, round to oval nuclei, stippled chromatin; (b) Immunohistochemistry (400×) with CD99 showing diffuse membranous staining; (c) H and E (400×) showing Homer-Wright rosette (small arrow), perivascular pseudorosette (big arrow), and frequent mitosis (arrowhead); (d) Immunohistochemistry (400×) showing retained INI-1 expression; (e) Immunohistochemistry (400×) showing negative staining for LIN28A; (f) EWSR1 break apart FISH showing split signals (one red and one green signal; one fused signal and red signal)EES accounts for <1% of all pediatric malignancies and incidence peaks around second decade with more than 80% of patients being diagnosed before 20 years of age.[2] Characteristic genetic abnormality in pPNET/ES is a fusion of EWS1 gene on chromosome 22q12 with another gene, most commonly (90–95%) with the FL11 gene on chromosome 11q24 forming t (11;22)(q24;q12) translocation causing dysregulation in cell proliferation, differentiation, apoptosis, angiogenesis, invasion, and metastases.[2,3] This genetic translocation forms the basis of the definitive diagnosis of an EES with FISH and reverse transcriptase polymerase chain reaction. pPNET/ES tumors need a multidisciplinary approach to treatment in order to bring out the best prognostic outcomes.[2] Cornerstone of therapy is maximal safe resection of the tumor followed by chemotherapy and adjuvant radiotherapy.[2] The standard chemotherapy agents are vincristine, ifosfamide, doxorubicin, and etoposide.[4] Intracranial ESS is a rare locally aggressive tumor and requires a dedicated multimodality treatment approach. Consent Consent from the patient was taken. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.