Rare serosal cystic gastric gastrointestinal stromal tumor with extensive intestinal metaplasia in an adherent gastric mucosa; a case report in a 65-year-old male.

Gastrointestinal (GI) intestinal stromal tumors account for 60% of mesenchymal GI tract tumors commonly located in the stomach and small intestine, predominantly solid tumors that rarely undergo cystic degeneration. A 65-year-old patient with increasing upper abdominal swelling and a computed tomography scan abdomen showed a large unilocular 17 × 16 × 15 cm lesion. A colossal cystic swelling in the lesser omentum, anterior to the stomach, was found upon exploration. Histopathological examination showed a spindle cell tumor turned out to be CD117 positive and S100 negative on immunostains. The tumor was moderate risk gastric gastrointestinal intestinal stromal tumor (GIST) based on the site; Stomach, Size >10 cm; Mitosis <5/5 mm2 according to risk assessment of GIST, 2006. GISTs are predominantly solid tumors and rarely undergo cystic transformation. The primary differential diagnoses of spindle cell neoplasm are GISTs, Leiomyoma, Leiomyosarcoma and Schwannoma. These spindle cell neoplasms are differentiated by applying a panel of Immunohistochemical stains, CD117, SMA and S100.