An Incidental Malignant Gastrointestinal Neuroectodermal Tumor of the Stomach: A Rare Case Report and a Literature Review.

Gastrointestinal neuroectodermal tumors (GNETs) are malignant tumors frequently arising within the muscularis propria of the gastrointestinal tract and often extend into the submucosa and subserosa. The stomach is the second most common site of incidence of GNETs after the small intestine. The most important differential of GNET is the clear cell sarcoma-gastrointestinal (CCS-GI). Both share similar morphological as well as molecular features and show S100 positivity; however, the lack of melanocytic differentiation in GNET distinguishes it from CCS-GI. Both typically show rearrangements of the EWSR1 gene, with t(12;22) (q13;q12) EWSR1-ATF1 or t(2;22) (q34;q12) EWSR1-CREB1 fusions. We present a case of a 71-year-old man with an incidentally discovered GNET in the gastric cardia and fundus.