Abstract
BACKGROUND: Capicua transcriptional repressor-double homeobox 4 sarcoma (CDS) is a rare and aggressive malignant soft tissue tumor that typically arises within the soft tissues. We report an exceptionally rare case of a gastric CDS successfully resected despite its extensive invasion into surrounding organs. CASE PRESENTATION: A 48-year-old male presented with a progressively enlarging abdominal mass. Upper gastrointestinal endoscopy revealed a large ulcerative tumor on the posterior gastric wall. Biopsy results initially suggested a neuroendocrine cell carcinoma. Contrast-enhanced computed tomography showed a 20 cm tumor protruding from the posterior stomach wall, directly invading the pancreas and colon. We performed a multivisceral resection (stomach, pancreatic tail, spleen, and transverse colon) achieving an R0 resection. Pathological examination of the permanent specimen revealed small round cells with high nuclear-to-cytoplasmic ratios. Immunohistochemical staining confirmed the diagnosis of CDS. The patient recovered well and was discharged on postoperative day 33. CONCLUSIONS: This case report describes the first detailed account of a surgically resected aggressive CDS originating from the stomach.