Invasive Lobular Breast Cancer Presenting an Unusual Metastatic Pattern in the Form of Peritoneal and Rectal Metastases: A Case Report

Gastrointestinal metastases from invasive lobular breast cancer are uncommon with the stomach and small intestines being the most common metastatic sites. Peritoneal and rectal metastases are very rare and only rarely occur as the first manifestation of disease. We herein report the case of a 47-year-old woman who presented with abdominal carcinomatosis as a first sign of invasive lobular breast carcinoma (ILC). Identifying the most important immunohistochemical markers for ILC: gross cystic disease fluid protein 15, estrogen and progesterone receptors enabled a correct diagnosis. After a six year disease-free period, relapse occurred with severe obstruction due to rectal metastasis from lobular breast carcinoma. Since there was no widespread metastatic disease, surgery with concomitant hormonal therapy was performed.