Primary monophasic synovial sarcoma of the duodenum confirmed by cytogenetic analysis with demonstration of t(X;18): a case report.

: Synovial sarcoma (SS) is an uncommon malignant neoplasm of the soft tissues. It mainly affects the periarticular tissues of the extremities in young adults, but has been described at nearly all sites; nevertheless, the gastrointestinal tract is an exceptional location. We report a case of a primary synovial sarcoma of the duodenum in a 69-year-old woman. Histological study showed a monophasic pattern. The tumor cells demonstrated diffuse vimentin and Bcl-2 expression, partial EMA expression and focal AE1/3 positivity. The differential diagnosis includes gastrointestinal stromal tumors. Cytogenetic analysis confirmed the diagnosis, with detection of the X;18 translocation. The patient presented postoperative complications and died one month following the intervention.