Jejunal GIST: A Case Report of Incidentally Detected in A Patient with Breast Cancer

Gastrointestinal stromal tumors (GISTs) represent the most prevalent mesenchymal neoplasms of the gastrointestinal (GI) tract, typically originating in the stomach (60%) and small intestine (30%). Among the segments of the small intestine, the jejunum is a relatively uncommon site for GIST occurrence. The coexistence of GISTs in patients with a prior history of breast cancer is exceedingly rare, and poses a unique diagnostic and therapeutic challenge due to the possibility of metastatic disease versus a second primary tumor. We present the case of a 55-year-old female with a prior diagnosis of breast carcinoma, who was incidentally found to have a jejunal mass during routine oncologic surveillance. Radiological and endoscopic evaluations raised suspicion for a submucosal tumor, which was subsequently confirmed as a jejunal GIST via histopathological and immunohistochemical analysis following surgical resection. The patient underwent curative segmental jejunal resection with negative margins and had an uneventful postoperative recovery. Risk assessment based on size and mitotic index placed the tumor in a low-risk category, and no adjuvant therapy was deemed necessary. This case highlights the importance of considering GISTs in the differential diagnosis of incidental small bowel masses, especially in patients with a history of malignancy, and underscores the role of complete surgical excision in achieving curative outcomes.