High intestinal obstruction secondary to peritoneal metastases from invasive lobular breast carcinoma: A case report of an unusual presentation.

Gastrointestinal metastases from breast cancer are uncommon and occur more frequently in invasive lobular carcinoma (ILC), which exhibits a distinctive metastatic pattern involving the peritoneum, mesentery, and gastrointestinal tract. These metastases may present with nonspecific symptoms or with bowel subobstruction and obstruction, making diagnosis challenging, particularly in the absence of obvious intramural lesions on imaging studies. We report the case of a 64-year-old woman with a history of bilateral mastectomy for ILC who presented with abdominal pain, nausea, and vomiting suggestive of proximal intestinal obstruction. Upper gastrointestinal endoscopy demonstrated a severe, non-passable stenosis of the third portion of the duodenum. Contrast-enhanced CT and MRI demonstrated ill-defined enhancing peritoneal and mesenteric lesions involving the transverse mesocolon and mesenteric root, with extrinsic compression of the third and fourth portions of the duodenum and no definite primary intramural bowel mass. MRI demonstrated restricted diffusion within the lesions, and 18F-FDG PET/CT showed increased FDG uptake at the mesenteric root and transverse mesocolon. Exploratory laparoscopy with biopsy confirmed metastatic invasive lobular breast carcinoma involving the transverse mesocolon. Peritoneal metastases from ILC may cause extrinsic compression of the gastrointestinal tract and present as bowel obstruction even in the absence of radiologically detectable masses. In patients with a history of breast cancer who develop gastrointestinal symptoms, peritoneal metastatic disease should be included in the differential diagnosis. A multidisciplinary approach integrating endoscopy, advanced imaging, and histopathological confirmation is essential for accurate diagnosis and appropriate management.