In 1921, James Ewing firstly reported Ewing's sarcoma (ES), and in 1969 Tefft reported extraosseous-Ewing's sarcoma(EES)/peripheral primitive neuroectodermal tumors (pPNETs). EES is a malignant tumor derived from neuroectodermal that is clinically diagnosed as a pPNET,and considered a special clinical manifestation of ES. EES/pPNETs are small, blue, round cells from neural crest cells, and all of them belong to the Ewing's sarcoma family. pPNET often occurs in the deep soft tissues of the trunk, paravertebral, lower limbs and retroperitoneum, and can be also found in the kidney, pancreas, ovaries and testes. [4, 5] It is rare in the head and neck, especially in the larynx.
There is no characteristic clinical presentation of pPNETs, the main manifestations are only related to tumor location, size, and invasiveness. The images and serum biomarkers are also nonspecific. On CT images, the tumor’s density was uniform or heterogeneous, and the size of tumors depends on where they are located. The boundaries between the lesion and adjacent tissues are unclear. Maximum intensity projection image reconstruction can show tortuous blood vessels in tumors on enhanced CT images. On MRI images, most tumors have isointense to slightly hyperintense T1-weighted signal and heterogeneous hyperintense T2-weighted signal,and have obvious enhancement when enhanced scan. On fluid-attenuated inversion recovery images, the lesion mixed high signal intensity. [7, 8] However, intra-tumoral calcification was rare in pPNETs.
Because of unspecific clinical manifestations, the diagnosis of pPNETs mainly depends on histopathology. Under the light microscope, small blue round cells in tumor are visible, they are tightly arranged in cords or nests to form rosettes and pseudorosettes (Homer-Wright rosettes). In cytogenetics, almost all of pPNETs are defined by translocation of chromosome 22, a fusion of the Ewing's sarcoma breakpoint protein (EWS/EWSR1), located at 22q12, and a gene of the erythroblast transformation-specific (ETS) family of transcription factors. In approximately 90% of pPNETs, the fusion gene is EWS-FLI1, which formed by a chromosomal translocation t (11;22) (q24; q12). FLI1, located at 11q24, is one of the members of the ETS family. In approximately 10% of pPNETs, the fusion gene is EWS-ERG, by translocation t (21;22) (q22; q12), which results in fusion of the EWS gene on chromosome 22 to the ERG gene on chromosome 21. Here, the ERG gene substitutes for FLI1. In addition, there are a small number of ETS family genes, such as ETV1 (7p22) and E1AF (17q12), which form fusion genes with EWS. Immunohistochemically, ES/pPNETs strongly express the membranous immunostaining of CD99 that is sensitive but not specific. CD99 is almost always present in these tumors. As reported, the positivity of CD99 is in up to 92%. FLI-1, one of the ETS family transcription factors, is highly expressed in ES/pPNETs. It has been reported that the protein expression in over 70% of ES/PNET with a specificity of over 90%. Therefore, it suggests that antibodies to FLI-1 may play a very valuable role in the diagnosis of ES/PNET.[13, 14] Due to the high sensitivity of CD99 and the high specificity of FLI-1, Sarah Chiang et al.considered the tumor, showed both membranous CD99 and nuclear FLI-1 expression, was more likely to harbor an EWSR1 rearrangement, and this is consistent with ES/pPNETs. Currently, an important basis on the diagnosis of ES/pPNETs is the presence of at least two neuromarkers in the Homer-Wright chrysanthemum structure or/and immunohistochemistry.
pPNETs are usually treated with a combination of surgery, radiotherapy and chemotherapy. Surgery should completely remove the tumor as much as possible. Chemotherapy may use the CAV-IE regimen with vincristine–pirarubicin–cyclophosphamide (CAV) and ifosfamide-etoposide (IE) alternately. Radiotherapy should be based on the age of the child, the size and location of the tumor, the response to chemotherapy, the type of histology and residual lesions. The radiation dose usually ranged from 30 to 66 Gy.
pPNETs deteriorate rapidly and have poor prognosis. Jurgens et al.  reported a 3-year disease-free survival rate of 56% (± 11%). Patients with pPNET often developed distant metastases and local recurrence within 2–3 years after surgery. It is well known the pPNETs of the parapharyngeal space are extremely rare. Lu reported a similar case of cervical ganglioneuroblastoma of the parapharyngeal space with progressive inspiratory dyspnea and dysphagia in a 4-year-old female,the girl was treated with surgery and remained healthy for more than one year. Another similar case of an 8-year-old girl was reported by Divya Khosla. Although after chemotherapy and radiotherapy treatment, but she eventually died of lung and brain metastasis due to the deterioration of the disease.
Because ES/pPNETs have non-specific clinical manifestations, it is easy to cause misdiagnosis if pediatricians lack an understanding of them. The case we reported was misdiagnosed by pediatricians in many hospitals as speech retardation, sinusitis and adenoid hypertrophy, due to slurred speech and sleep snoring. When the diagnosis was made, the tumor had been getting huge. This lesson cannot be forgotten. Therefore, for a child who is slurred speech and snoring, we should not only think of hypertrophied tonsils and adenoids, but also tumors in oropharynx. It is necessary to give CT or MRI examination on head, neck or chest, so as not to take a misdiagnosis of the disease.