Frequency of Translocation t(11;22)(q24;q12) Using Fluorescence In Situ Hybridization (FISH) in Histologically and Immunohistochemically Diagnosed Cases of Ewing's Sarcoma.

Introduction Ewing sarcoma (ES) family of tumors is one of the most common groups of malignancies arising in children, adolescents, and young adults. Although characteristic histology with immunohistochemical expression of CD99 and FLI1 after exclusion of other small round blue cell tumors is considered diagnostic of ES, frequency of typical ES translocation, i.e., t(11;22)(q24;q12) is not known in our population. Therefore, in this study, we aimed to evaluate the frequency of this translocation in histologically and immunohistochemically diagnosed cases of ES along with its association with other pathological parameters. Methods A total of 43 morphologically and immunohistochemically diagnosed cases of ES were included in the study. Fluorescence in situ hybridization (FISH) was performed on representative paraffin blocks to identify t(11;22)(q24;q12) translocation. Association with various clinicopathological characteristics was determined. Results Mean age of the patients was 18.23±9.57 years. Bone was the most commonly involved site (22; 51.2%) followed by soft tissue (17; 39.5%) and parenchymal organs (4; 9.3%). A total of 88.4% of cases were found to be FISH-positive for t(11;22)(q24;q12). No significant association of translocation positive cases was noted with tumor size or disease-free survival. Similarly, no significant association of tumor size with disease-free survival was found. Conclusions A significant proportion of cases of histologically diagnosed cases of ES exhibited characteristic t(11;22)(q24;q12). This signifies that histology along with immunohistochemistry is reliable for the diagnosis of this tumor; however, in difficult cases, FISH can be performed to detect characteristic translocation. Moreover, we did not find tumor size to be a significant prognostic indicator of survival in ES.