Breast Cancer Metastasis Masquerading as a Primary Gynecological / Colonic Malignancy: A Rare Diagnostic Conundrum.

Breast cancer is the most common malignancy affecting women. Metastatic involvement of the gastrointestinal (GI) tract secondary to a primary breast malignancy is rare. Here, we describe the case of a 60-year-old woman with a history of right lobular breast cancer (diagnosed and treated five years prior to presentation) who presented with fatigue, generalized abdominal pain, distension, weight loss, and vomiting. Her initial imaging was suspicious for a primary gynecological malignancy; however, subsequent workup showed a colonic mass. Total colonoscopy revealed colon metastases, and an immunohistochemical profile favored invasive lobular carcinoma of breast. Most cases of gastrointestinal metastases from breast cancer have lobular histology; however, colonic involvement is rare.