Gastrointestinal autonomic nerve tumor presenting as high-grade sarcoma. Case report and review of the literature.

Gastrointestinal autonomic nerve (GAN) tumors, also known as plexosarcomas, are a rare distinct subtype of the gastrointestinal stromal tumors. These tumors are usually histologically low-grade, epithelioid or spindle-cell neoplasms that can be distinguished from the other gastrointestinal stromal tumors on the basis of their unique ultrastructural features. A 66-year-old female presented with a histologically high-grade sarcoma of the small bowel. Ultrastructural studies showed features of a GAN tumor. The light microscopic and ultrastructural features are described. The tumor cells gave strong, diffuse staining for vimentin and synaptophysin, and weak focal staining for neuron-specific enolase and S100. While usually presenting as low-grade neoplasms on histologic examination, this case demonstrates that GAN tumors should be considered in the differential diagnosis of a histologically high-grade sarcoma of the gastrointestinal tract, especially when evidence of smooth muscle, peripheral nerve sheath, or neuroblastic origin is not forthcoming.