From the Unexpected: Unveiling the Diverse Presentations of Extraosseous Ewing's Sarcoma.

Extraosseous Ewing's sarcoma (EES) is a rare but aggressive soft tissue malignancy of small round blue cells and commonly poses a diagnostic challenge because of its nonspecific anatomical locations and association with other neoplasms. This series of cases presents five uncommon presentations of EES in adult patients in the form of tumors present in the mediastinum, mesentery, right suprarenal gland, infraclavicular soft tissue, and prostate. The clinical presentations varied from rapidly worsening respiratory failure caused by a mediastinal tumor to a preoperatively misdiagnosed gastrointestinal stromal tumor that was subsequently diagnosed as EES post-surgery. Immunohistochemistry (IHC) was crucial in diagnosis, and all the cases were strongly positive for CD99 with supporting markers such as NKX2.2 and FLI-1. Multimodal treatment with chemotherapy (vincristine, doxorubicin (adriamycin), cyclophosphamide, ifosfamide, and etoposide (VDC-IE) regimen), surgery, and radiotherapy was used, and results were variable, with one patient dying of neutropenic sepsis and others having a favorable response to therapy with follow-up. This series puts forward the significance of keeping EES in the differential diagnosis of adult deep-seated or visceral soft tissue masses and the imperative need for prompt histopathological and immunohistochemical correlation to aid proper management.