I.V. Boulytcheva, Cosimo Sciotto, Yu.N. Soloviev, M.D. Aliev, N.E. Kushlinskii

Ewing family tumors (Ewing sarcoma/primitive neuroectodermal tumor ES/PNET) are rare sarcomas of bone and soft tissue. Although ES and PNET were originally considered to be separate entities, those tumors are universally regarded now as a common histological entity. ES and PNET share a balanced translocation (11;22)(q24;q12) in over 90 % of cases with others having variant translocations. With team approach and current treatment modalities the 5-year survival rate for "Ewing family tumors" (EFT) is over 60 %. Even though Ewing-s sarcoma arises chiefly in children and young adults we included in our study 46 bone and soft issue cases from adult clinic. The majority of tumor cases (78 %) originate in the bone. The "gold standard" for diagnosis of EFT is the combination of cytogenetic and/or molecular genetic techniques. However, these techniques were available only in 41 % of our cases, in others, the diagnosis was made based on morphology and immunohistochemistry (IHC) only. IHC was performed including CD99, FLI1, Desmin, pancytokeratins AE1/AE3, chomogranin and synaptophysin, in 20 cases the IHC panel was limited to CD99. Histologically, the majority of cases (86 %) showed only typical features of ES, 10% cases were signed out as PNET with rosette formation and positive neuroendocrine markers, 5 % of cases showed prominent spindle cells and intersecting fascicles, 2 % of cases were characterized by abundant hyalinization of matrix and classified as sclerosing type and 1 % of cases as atypical (large cell). We did not recognize "adamantinoma-like" sarcoma in our series. The majority, but not all ES/PNET tumors can be diagnosed using morphologic criteria and ancillary IHC. Genetic confirmation is essential for the diagnosis, especially in cases with unusual histology. Molecular genetic techniques are available now in both adult and pediatric clinics in Moscow, this part of research has been extended and the results are pending. Nowadays, oncologists, especially in pediatric practice, do not accept the diagnosis of EFT without genetic and cytogenetic confirmation. The goal of this study is to evaluate the follow-up in a large group of patients, obtain the genetic confirmation when it is missing, investigate in detail the unusual cases, for example cytokeratin and desmin positive, spindle cell and large cell variants or "adamantinoma-like" tumors.