Simultaneous Gastric Cancer Metastases to the Small and Large Intestines: Hidden Small Intestinal Lesions and Colonic-Mimicking Metastases.

[INTRODUCTION] Gastric cancer often presents with metastases at diagnosis, but simultaneous metastases to both the small and large intestines are extremely rare and may be misinterpreted as synchronous primary intestinal cancers, particularly when preoperative imaging is inconclusive.

[CASE PRESENTATION] A 78-year-old male receiving cabozantinib for hepatocellular carcinoma with vertebral metastasis presented with anorexia, epigastric discomfort, and melena. Endoscopy revealed an ulcerative gastric lesion, and colonoscopy showed irregular ulcerative lesions in the ascending and transverse colons. The patient underwent laparoscopic distal gastrectomy, right hemicolectomy. During surgery, a small intestinal tumor was suspected, prompting an additional partial resection. Histopathology and immunohistochemistry (CK7, CK20, CDX2, SATB2, Arginase-1) confirmed that the intestinal lesions were metastases from gastric cancer rather than synchronous primary colorectal cancers.

[CONCLUSIONS] This case suggests that preoperative and intraoperative imaging may not detect rare metastatic patterns, and that immunohistochemical analysis may help estimate tumor origin. Careful differentiation between true synchronous colorectal cancer and gastric cancer with intestinal metastases may help guide treatment decisions.