Adamantinoma-like Ewing Sarcoma Arising in the Abdominal Cavity: A Case Report of a Rare Entity and Review of the Literature

Abstract ALES is a rare subtype that demonstrates the EWSR1-FLI1 translocation characteristic of ES and demonstrates complex epithelial differentiation including diffuse cytokeratin and p40 expression. It has predominantly recognized in the head and neck and is common in middle-aged population. This case is the first case of ALES reported in the abdominal cavity, sharing some morphological characteristics with ALES in the head and neck, including monotonous cytology, infiltrative growth pattern, and complex epithelioid differentiation, but ALES in the head and neck often has high-grade histological features (e.g., necrosis, high mitotic rate, etc.), and sudden keratinization can also occur, but these features were not reflected in this primary abdominal cavity ALES. Although ALES arising in the abdominal cavity and in the head and neck sites share the immunohistochemical and molecular profile, our case can provide new ideas in differential diagnosis of ALES arising in abdominal cavity and promote increased recognition and understanding of ALES.