[Clinical and morphological characteristics of Ewing's sarcoma and the algorithm for diagnosing undifferentiated round cell sarcomas]. / Kliniko-morfologicheskaya kharakteristika sarkomy Yuinga i algoritm diagnostiki nedifferentsirovannykh kruglokletochnykh sarkom.

BACKGROUND: The group of undifferentiated round cell sarcomas, according to the World Health Organization Classification, in addition to Ewing's sarcoma (ES), includes round cell sarcoma with rearrangement of the EWSR1 gene with partners not from the ETS gene family, sarcoma with BCOR gene alterations, CIC -rearranged sarcoma. Despite the fact that all tumors have clear histological and immunological criteria, their diagnosis can be difficult, given the fact that there are overlapping variants of the morphological picture and immunophenotype both within the group and with other round cell tumors. OBJECTIVE: Present a comparative analysis of genetically verified ES, sarcoma with BCOR gene alterations and CIC-rearranged sarcoma. MATERIAL AND METHODS: A comparative study of biopsy specimens of bones, soft tissues and internal organs was carried out in 118 patients with ES, 10 with BCOR gene alterations and 8 with CIC-rearranged sarcomas. All cases were genetically verified. The following research methods were used: histological, immunohistochemical, RT-PCR, RNA sequencing and FISH. RESULTS: Within our cohort, it was shown that ES predominantly affects bones, while soft tissue localization is more typical for the other two undifferentiated round cell sarcomas. Histologically, in the overwhelming majority of cases, ES is characterized by a monomorphic round-cell structure; on the contrary, heterogeneous structure is typical for sarcoma with alterations of the BCOR gene, CIC-rearranged sarcoma. High sensitivity and specificity of CD99/NKX2.2 co-expression for ES, BCOR/SATB2/TLE1 for sarcoma with BCOR gene alterations, high specificity and low sensitivity of WT1/ETV4 co-expression for CIC-rearranged sarcoma was shown. CONCLUSION: For the differential diagnosis of undifferentiated round-cell sarcomas, it is necessary to take into account the clinical, morphology when compared with the data of the IHC study, and verification by molecular genetic methods is necessary to improve the accuracy of diagnosis.

[«Malignant stroma?¼ Alternative localization of classical genetic aberrations in neuroblastoma]. / Zlokachestvennaya stroma? Al'ternativnaya lokalizatsiya klassicheskikh geneticheskikh aberratsii v neiroblastome.

Neuroblastoma (NB) is a malignant neoplasm originating from the primary cells of the sympathetic nervous system. Patients with NB are risk-stratified using a number of features including age at diagnosis, disease stage, tumor histology and genetic profile (status of NMYC, ALK genes, regions 1p and 11q). The interpretation of the results of genetic studies can become a source of problems because neuroblastoma has a heterogeneous histological pattern. The article describes 2 cases with classical for NB chromosomal aberrations in the stromal component of the tumor.

[CIC-rearranged sarcoma: a case report and literature review]. / CIC-perestroennaya sarkoma: klinicheskoe nablyudenie i obzor literatury.

CIC-rearranged sarcoma is a rare and extremely aggressive tumor that occurs mainly in soft tissues. Despite the fact that identification of a characteristic genetic rearrangement is necessary to verify the diagnosis, in most cases, the correct diagnosis can be made by comparing histological signs and a characteristic immunophenotype, which greatly speeds up the diagnosis. The article describes a case of CIC-rearranged sarcoma in a 14-year girl with the successful application of the CWS-2009 treatment protocol.

[Rhabdomyosarcomas: structural distribution and analysis of an immunohistochemical profile]. / Rabdomiosarkomy: strukturnoe raspredelenie i analiz immunogistokhimicheskogo profilya.

Rhabdomyosarcoma (RMS) is a malignant soft tissue tumor originating from primitive mesenchymal cells, which is most common in children. OBJECTIVE: To qualitatively and quantitatively assess the expression of myogenic transcription factors on a large sample, to identify potential phenotypic differences, and to estimate the distribution and frequency of aberrant markers, such as ALK, PAX5, WT1, PCK, CAM5.2, SIX1, and Synaptophysin. MATERIAL AND METHODS: The investigation included 202 tumor tissue samples. Five tissue microarrays were assembled from the obtained material for subsequent histological and immunohistochemical studies. RESULTS: Embryonal RMS (ERMS) was diagnosed in 103 cases; alveolar RMS (ARMS) was detected in 80; spindle-cell/sclerosing RMS (SRMS) was found in 16 cases; epithelioid RMS (EpiRMS) was diagnosed in 2 patients. The expression of Myogenin and MyoD1 was detected in all the examined RMS tissue samples. ARMS was more characterized by staining at 1+ and 2+ intensities; at the same time, more than 50% of ERMS, SRMS, and EpiRMS cases showed staining at 1+ intensity. ALK expression was investigated using the D5F3 and p80 clones. The D5F3 clone displayed a higher staining intensity than the p80 clone (p<0.05). The expression of PAX5 was observed in 13 of 75 ARMS cases. That of WT1 and SIX1 was found in all RMS groups. CONCLUSION: The morphological diagnosis of RMS requires a careful assessment of all of the above factors, especially taking into account the variability in the expression of myogenic transcription factors and the high level of phenotypic aberration.