Gastrointestinal autonomic nerve tumor: immunohistochemical and molecular identity with gastrointestinal stromal tumor.

Gastrointestinal autonomic nerve tumor (GANT) is a gastrointestinal neoplasm that ultrastructurally recapitulates the enteric neural plexus. This study identifies and defines the features of 10 cases of this rare mesenchymal tumor and compares its clinicopathologic and molecular genetic features with the data on gastrointestinal stromal tumor (GIST). The majority of patients in this series presented at an older age (mean 64 years). Tumors arose from the stomach (6), small intestine (2), and retroperitoneum (2). Mean tumor size was 14 cm; however, four neoplasms were <6 cm. Histologically, tumors were spindled or epithelioid; one epithelioid tumor demonstrated a previously undescribed rhabdoid histologic phenotype. All tumors were positive for CD117 (KIT), while eight of 10 were positive for CD34. In contrast, only two were positive for S-100, and all were negative for actin and desmin. Five GANTs demonstrated GIST-specific gain-of-function mutations in the juxtamembrane domain of the c-kit gene (50%). Three of 10 patients died of disease in 22-30 months, one patient died in the postoperative period, and one patient died of complications of CML. The clinicopathologic, histologic, immunohistologic, and molecular features of GANT are similar to GIST, indicating that GANT merely represents a phenotypic variant of GIST.