Rare Occurrence of Colorectal Adenocarcinoma in Association with Periampullary GIST: A Case Report with Systematic Review

Introduction Colorectal cancer is highly prevalent globally and remains a leading cause of cancer-related mortality. Gastrointestinal stromal tumors (GISTs) are rare mesenchymal neoplasms. The synchronous occurrence of colorectal adenocarcinoma and small bowel GIST is exceptionally rare, making such cases noteworthy for their diagnostic and management implications. These tumors are typically detected incidentally, with the underlying mechanisms remaining unclear. This report presents a rare case of colorectal adenocarcinoma associated with a synchronous duodenal GIST and includes a literature review to examine potential links and relevant management considerations. Case presentation A 43-year-old woman presented with nonspecific symptoms and severe microcytic anemia (hemoglobin 4.9 g/dL). Imaging and biopsy identified concurrent non-obstructing sigmoid colon adenocarcinoma and a periampullary GIST, an unusual co-occurrence. The patient underwent staged surgery: laparoscopic sigmoidectomy with primary anastomosis (stage III), then pancreaticoduodenectomy one month later. The patient is planned for adjuvant chemotherapy, followed by three years of imatinib. Discussion Gastrointestinal stromal tumors (GISTs) are common. Most GISTs occur sporadically or as part of hereditary syndromes. Increasing reports describe synchronous GISTs found with other primary malignancies, suggesting possible shared factors. Coexistence with colorectal adenocarcinoma remains rare. Emerging molecular data suggest biological overlap between GIST and colorectal cancer molecular subtypes. Accurate staging and multidisciplinary planning are critical. Staged surgical resection may reduce operative morbidity. Conclusion Gastrointestinal stromal tumors (GISTs) have been identified in association with synchronous or metachronous tumors. A deeper understanding of this association is essential to reveal potential linkages and optimize management. Therefore, continued research remains a priority.