Multiple gastrointestinal metastases in de novo invasive ductal carcinoma of the breast: A case report and literature review.

Gastrointestinal tract (GIT) metastases occur in only 0.6% of metastatic breast cancer cases, with invasive lobular carcinoma being the predominant histological subtype. Synchronous GIT metastases at the time of invasive ductal carcinoma (IDC) diagnosis are exceptionally uncommon. We report a case of de novo IDC presenting with synchronous, multifocal metastases in the stomach and colon. The diagnosis was prompted by significantly elevated tumor markers and confirmed via endoscopic examination and biopsy. This case underscores the rarity of GIT metastases, particularly in IDC, and highlights the critical need for a high index of suspicion in the face of markedly elevated tumor markers, even without gastrointestinal symptoms. While contrast-enhanced computed tomography has limited sensitivity for detecting small GIT lesions, endoscopic biopsy with immunohistochemical analysis remains the gold standard for diagnosis. Accompanying this report is a systematic literature review on breast cancer metastases to the GIT.