Rectal Metastasis from Breast Cancer: A Case Report and Review of Literature

Background Metastatic spread of breast cancer to the gastrointestinal (GI) tract is very uncommon (< 1 % of all metastases), but it is disproportionately higher in invasive lobular carcinoma (ILC) compared to invasive ductal carcinoma (IDC). Its presentation can mimic primary rectal malignancy, often leading to delayed diagnosis. Case presentation We describe a 40-year-old woman with metastatic, hormone-receptor–positive classic ILC who developed rectal obstruction two years after her breast-cancer diagnosis. Initial colonoscopy with superficial biopsies were negative. One year later, pelvic MRI demonstrated smooth, concentric thickening of the rectal wall; repeat biopsies confirmed metastatic lobular carcinoma. Discussion This case illustrates the diagnostic challenges posed by rectal metastasis from ILC. Because tumor cells infiltrate submucosa and muscularis before reaching the mucosa, up to one-quarter of initial rectal biopsies are falsely negative. Imaging, especially MRI and EUS, provide important information about initial mucosal sparing. Endoscopic and radiologic features often mimic primary rectal pathology, underscoring the importance of deep biopsy and imaging in establishing the diagnosis. Conclusion New lower-GI symptoms in any breast-cancer survivor, especially one with ILC, should prompt pelvic MRI and deep tissue sampling to exclude metastatic disease if superficial biopsies are negative.