Gastric metastasis from colorectal cancer: an updated comprehensive review of epidemiology, mechanisms, diagnosis, and management.

Colorectal cancer (CRC) is one of the most common and deadly malignancies worldwide, with metastasis being its most lethal feature. Although the liver and lungs are well-recognized sites of metastasis, gastric involvement as a target organ is extremely rare. The exact incidence remains unclear due to the lack of large-scale epidemiological data, and existing literature consists mainly of case reports and empirical risk estimates. This rarity, combined with the frequent misdiagnosis of gastric metastases as primary gastric cancer in clinical practice, makes gastric metastasis from CRC a unique clinical entity characterized by diagnostic challenges and therapeutic difficulties. Analysis of available case reports indicates that the median age at onset is approximately 65 years, with the left-sided colon being the most common primary site. The interval between diagnosis of the primary tumor and development of gastric metastasis ranges from 6 months to 10 years. Diagnosis primarily relies on a combination of immunohistochemical markers-CK7-/CK20+/CDX2+-while the emerging marker SATB2 further enhances diagnostic specificity. Currently, there is limited high-level evidence-based guidance for treatment; systemic chemotherapy regimens used for metastatic CRC-such as FOLFOX or FOLFIRI combined with targeted therapy-are typically employed. Surgical resection may be considered for isolated, resectable gastric metastases, but overall prognosis remains poor, with a median survival of approximately 12 months. This review comprehensively summarizes the epidemiological characteristics, molecular mechanisms, clinicopathological diagnosis, routes and mechanisms of metastasis, clinical manifestations, diagnostic strategies, differential diagnosis, treatment options, and prognostic factors associated with gastric metastasis from CRC, aiming to provide clinicians with a comprehensive understanding of this rare condition and to serve as a reference for future research and clinical practice.