Primary Ewing's sarcoma of the small intestine

Area of Science:

• Oncology
• Pathology
• Genetics

Background:

• Ewing sarcoma is a rare, aggressive small round blue cell tumor typically affecting pediatric and young adult patients, primarily in long bones.
• Intestinal involvement is exceptionally rare, often presenting with non-specific symptoms like abdominal pain and fatigue.

Observation:

• A 17-year-old female presented with abdominal pain due to a large pelvic mass initially suspected to be ovarian.
• Surgical exploration revealed the mass originated in the ileum, necessitating resection of the affected intestinal segment.

Findings:

• Histopathological examination showed a neoplasm of small round cells with characteristic morphology.
• Immunohistochemical analysis revealed tumor cell reactivity for CD99 and ERG, with negativity for cytokeratins, FLI1, WT1, DOG1, and lymphoid markers.
• Fluorescence in situ hybridization (FISH) confirmed EWSR1 gene rearrangement, a hallmark of Ewing sarcoma.

Implications:

• This case underscores the importance of considering Ewing sarcoma in the differential diagnosis of ileal masses, even in the absence of typical bone involvement.
• The findings emphasize the utility of integrating morphological, immunohistochemical, and molecular data for accurate diagnosis of rare extraosseous Ewing sarcomas.
• Optimal management involves surgical resection of the involved ileal loop followed by adjuvant chemotherapy.