Malignant Neoplasms in Children: Clinical Manifestations and Diagnosis Maxim Treatment efficacy for children with cancer depends on the diagnosis timeliness since the earlier expert care has been started, the higher likelihood there is to achieve remission. In this regard, a special role belongs to primary care physicians — district pediatricians who should timely recognize the malignant neoplasm and refer the patient to a pediatric oncologist for advice. Wherein, a limited number of primary patients and atypical course of oncological diseases are the causes of a decrease in oncological alertness. This lecture is aimed at a wide range of specialists (pediatricians, radiologists, pathologists) and devoted to clinical manifestations and diagnosis of malignant neoplasms in children — hemoblastosis and solid tumours. The suggested algorithms for the examination of patients will allow to make a diagnosis faster and timely initiate expert care in specialized departments. The article is illustrated with unique pictures — images of histological specimens, MRI, and CT of patients with the most neglected cases of malignant neoplasms being the result of diagnostic errors of pediatricians.