A rare case of extraskeletal Ewing Sarcoma of the small bowel presenting as intussusception: a case study and review of literature

Ewing Sarcoma is a common round cell sarcoma of pediatric patients arising in bone. Extraskeletal location is uncommon and small bowel wall is one of the rarer sites. Twenty-seven cases have been reported in published literature, exclusively arising from the small intestinal wall excluding the ones reported within the mesentery. We report a 45-year-old-man who presented with transient intussusception. After confirmation of a mass, right hemicolectomy was performed. The tumor identified in the ileum, infiltrated the wall through the submucosa, extending through muscularis propria into the subserosa. One of the regional nodes showed metastasis. On immunohistochemistry, the tumor cells were diffusely positive for CD99, CK 8/18 and NKX 2.2. The immunohistochemistry markers highlighted significant overlap between neuroendocrine neoplasm and Ewing Sarcoma. Molecular evaluation revealed the hallmark EWSR1-FLI1 fusion confirming the diagnosis. Extraskeletal Ewing Sarcoma of small intestines is rare and associated with overall poor prognosis. Immunohistochemistry shows considerable overlap with neuroendocrine carcinomas and molecular evaluation is prudent.