Breast Signet-ring Cell Lobular Carcinoma Presenting with Duodenal Obstruction and Acute Pancreatitis

We report here an extremely rare case of breast signet-ring cell carcinoma (SRCC) initially manifesting as duodenal metastasis and acute pancreatitis. A 62-year-old female presented with duodenal obstruction and swollen head of the pancreas, and the diagnosis of acute pancreatitis was initially made. Upper gastrointestinal endoscopy revealed duodenal stenosis with erosive mucosa, with signet-ring cells infiltrating the submucosal layer, suggesting duodenal metastasis of SRCC. Despite absence of a palpable mass in both breasts, computed tomography revealed diffuse enhancement of the left breast in addition to left axillary lymphadenopathy. Histological examination of mammary needle biopsy samples revealed SRCC with a non-invasive lobular carcinoma component. Primary breast SRCC with duodenal metastasis was therefore diagnosed. The patient underwent palliative surgery twice for intestinal obstruction due to peritoneal dissemination. She has remained alive without bowel obstruction for 18 months while being treated with cytotoxic chemotherapies.