Relevance: Peripheral primitive neuroectodermal tumor (PNET) belongs to the group of malignant tumors that develop from migrating embryonic neural crest cells. PNET includes several nosological forms: Askin's tumor, esthesioneuroblastoma, the very peripheral primitive neuroectodermal tumor, and Ewing's sarcoma [1]. PNET accounts for 3–9% of all soft tissue tumors and 19% of all soft tissue sarcomas in children [2, 3]. In Europe and the US, PNETs account for 3.4 cases per year per 1 million

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... ren below 15 years; in Kazakhstan – 0.6-1.2 cases per 1 million child population. Rapid tumor growth, malignancy, and early metastasis to other organs and systems predetermine the PNET's specific role in oncology [4]. The purpose was to improve the quality and availability of early sarcoma diagnostics in children in medical institutions of the general medical network. Results: 35 cases of peripheral PNET in children were analyzed. The age of the patients was 1.5 to 17 years, the average age – 9.3 years. Boys were 1.3 times more than girls. One patient (3.6%) had extra-skeletal tumor localization. Children with stage IIB prevailed – 46.4% of cases (13 children). Radiographical differentiation between Ewing's sarcoma and primary chronic or "healed" (antibiotic) acute hematogenous osteomyelitis in the initial phase of the process is almost impossible before the extraosseous soft tissue component is formed. The bone damage process is more often localized in the bone diaphysis and subsequently spreads to its metaphyses. Conclusion: PNET originates most often from the chest wall, so it is advisable to start the X-ray examination from the chest. In terms of radiation semiotics, PNET is similar to Ewing's sarcoma and Askin's tumor; therefore, an additional immunohistochemical study of the tumor tissue is required. An important indirect diagnostic criterion in Ewing's sarcoma is the predominance of the soft tissue component over the bone manifestations. Extended CT and MRI studies with contrast enhancement (chest, abdominal cavity, pelvis, and the primary lesion area) and skeletal scintigraphy are required to clarify the extent of changes, stage the tumor accurately, and assess the tumor dynamics after treatment. The above conclusions generally coincide with the available literature data.