Retroperitoneal schwannoma with features of gastrointestinal schwannoma. A case report.

A case of retroperitoneal schwannoma with histological features of gastrointestinal (GI) schwannoma occurring in a 67-year-old woman is reported. The tumor was composed of spindle cells with focal pseudoatypism and it showed several features typical of gastrointestinal-type schwannoma such as lymphocytic infiltration, peripheral cuff of lymphocytes, lack of Antoni A pattern, and absence of thick walled vessels. Immunohistochemically, the tumor showed diffuse reactivity for S100 protein and glial fibrillary acidic protein. The authors discuss a phenotypical similarity of the lesion with GI schwannoma as well as the possible existence of GI-type schwannoma outside the tubal GI tract.