Invasive Breast Carcinoma with Rectal Metastasis: Analysis of a Rare Case and Literature Review

Breast cancer is the most common cancer among women worldwide. It frequently metastasizes to regional lymph nodes, bones, brain, liver, and lungs, while other sites, particularly the gastrointestinal tract, are rare. We present a rare case of rectal metastasis from breast cancer in a 63-year-old patient treated in 2009 for right breast carcinoma classified as T2 (25 mm) N1 (29N+/30) M0, with surgery, chemotherapy, radiotherapy, and hormone therapy. In late 2023, 14 years later, she presented with symptoms of abdominal pain and rectal bleeding, in a context of significant weight loss. Rectal examination revealed an indurated, irregular aspect of the rectal walls. Colonoscopy showed a pathological rectum in its lower and middle parts, with an ulcerated mucosa stenosing the lumen, requiring biopsies. The primary or secondary nature could only be confirmed after pathological examination. Pathological examination of the rectal biopsy revealed features of metastasis from an invasive lobular breast carcinoma. Immunohistochemical (IHC) study confirmed the breast origin. Following endoscopy, local evaluation MRI concluded a tumor process of the lower, middle, and upper rectum classified as cT3NOMx. A CT scan and PET-CT were performed for distant extension assessment, which returned negative.This rare case of rectal metastasis from breast cancer, occurring 14 years after initial treatment, underscores the importance of prolonged clinical follow-up and multidisciplinary management in patients with a history of breast carcinoma, particularly invasive lobular type. The atypical presentation, combined with digestive symptoms, highlights the need for thorough differential diagnosis. The key contribution of immunohistochemistry in confirming the breast origin of the metastasis guided optimal therapeutic management. Advances in imaging and diagnostic techniques, such as MRI and PET-CT, play a crucial role in the detection and management of metastases. This case highlights the importance of integrating new technologies and personalized approaches to improve clinical outcomes and quality of life for breast cancer patients.