1508 A Rare Case of Lobular Breast Cancer With Metastasis to the Colon

Abstract

INTRODUCTION: Metastasis from infiltrating lobular cancer (ILC) preferentially involves bones, peritoneum and liver. Metastatic involvement of the gastrointestinal (GI) tract is very rare and if present usually involves the stomach and small intestine. Colorectal involvement is extremely rare. We present a rare case of an elderly female with a history of ILC who presented with GI symptoms that led to subsequent diagnosis of colon metastasis. CASE DESCRIPTION/METHODS: This is a 68 years old female diagnosed with ILC of the right breast six years ago treated with lumpectomy and chemotherapy. She also had peritoneal carcinomatosis. Six years later, she presented with abdominal pain and dark stools mixed with blood. CT scan of the abdomen showed ascites, peritoneal thickening and normal appearing bowel. Colonoscopy showed internal hemorrhoids, melanosis coli and erythema in the transverse colon (Figure 1). Biopsy from transverse colon revealed atypical cells in the lamina propria in “Indian file pattern” with Immunohistochemistry (IHC) positive for CK-7, mammaglobin and negative for CDX2. A positive CK7 and mammaglobin in the colon suggest ILC metastasis (Figures 2 and 3) whereas a negative CDX2 excludes primary colon cancer. She was started on palliative chemotherapy. DISCUSSION: Metastasis of ILC to the colon can manifest with a wide range of clinical and radiological features resembling various GI disorders. Further incidence of benign GI disorders in these patients is higher than metastasis, making the diagnosis a challenge. The presentation can range from asymptomatic abdominal mass to perforation, GI bleeding and obstruction. Radiology findings include normal appearing colon to diffuse or multifocal involvement, micro nodularity, tethering and stenosis. Colonoscopy with biopsy has moderate diagnostic yield especially in the absence of intraluminal lesion, and therefore in suspicious cases, a deep biopsy is indicated. Diagnosis is based on establishing similarities in the histology between a colon and breast tissue in terms of cellularity, growth pattern, hormonal status and IHC. ILC involves the layers of the colon in a “single file pattern” causing very subtle changes that can be missed on endoscopy. Treatment involves a multi-disciplinary approach including surgery, radiation and systemic therapy. Despite treatment colorectal metastasis from ILC has a poor prognosis with a median survival of 1-2 years.