Malignant Gastrointestinal Neuroectodermal Tumors: Clinicopathological and Prognostic Features of 96 Patients.

Purpose: Gastrointestinal neuroectodermal tumors (GNETs) are uncommon malignant tumors derived from ectodermal primitive neural cells. Patients and Methods: We retrospectively analyzed 2 GNET cases at our hospital and the remaining 94 cases in the literature to determine clinicopathological prognostic factors. Results: The patients had a mean age of 36 years and a median tumor size of 4.5 cm. A total of 67.0% of the tumors were located in the small intestine, and 76.4% of the patients presented recurrence or metastasis. There was a significant difference in sex and presence of osteoclast-like cells (P<0.01). Microscopically, most cells were round or short spindle-like in shape, with weak eosinophilic or clear cytoplasm. Neoplastic cells were always arranged in solid sheets, nests, and pseudoalveoli. Immunohistochemistry showed strong, diffuse S100 and SOX10 expression, with a complete absence of HMB45 and Melan-A expression. A total of 72.9% of the cases revealed genetic EWSR1 recombination, including our 2 cases. The median time to death and first metastasis was 61 months and 12 months, respectively. K-M analysis showed a great difference in survival according to lymph node invasion or distant metastasis (M+N), independent lymph node metastasis (N), lower histological grades (G2), and aggressive chemoradiotherapy (P=0.026, P=0.027, P=0.039 and P=0.037). However, independent T, independent M, and postoperative routine adjuvant therapy showed no statistical influence on overall survival or disease-free survival. Conclusion: GNET is a new entity distinct in its clinical, morphological, immunochemical, and genetic features. Radical excision, close follow-up and adjuvant therapy may be effective for prolonged survival.