S2832 Mucinous Signet-Cell Adenocarcinoma of the Ileum: A Diagnostic Challenge

Abstract

INTRODUCTION: Malignancies of the small intestine are rare, and signet-ring cell carcinoma is one of the rarest forms of adenocarcinoma that can arise in the small bowel. We present a rare case of a patient who originally presented with abdominal pain and radiographic findings suggestive of ileal congestion and question of an infective process concerning for Crohn’s disease (CD). After an extensive work-up including multiple colonoscopies and computerized tomography scans (CT), the patient underwent an exploratory laparotomy and resection of an ileocolic mass was positive for signet ring cell adenocarcinoma. CASE DESCRIPTION/METHODS: A 68-year-old woman with a new diagnosis of Crohn’s disease presented as a transfer for recurrent severe lower-abdominal pain and weight loss. The patient had initially presented to an outside hospital. Family history was positive for CD. The initial CT scan revealed wall thickening and fat stranding of the terminal ileum with right lower quadrant mesenteric lymph nodes. An initial colonoscopy showed a normal colon with superficial, linear erosions in the distal rectum. The patient’s bloodwork was pertinent for an elevated C-reactive protein and calprotectin. Given these findings, the patient was diagnosed with CD and treated. After multiple readmissions for similar pain and a repeat CT scan showing a possible abscess or phlegmon, the patient was transferred. Upon arrival, the patient was hemodynamically stable with unchanged labs. A repeat colonoscopy was performed and a biopsy of the terminal ileum showed mild inflammatory changes and congestion. The pathological analysis confirmed the presence of SRCC. The patient underwent an esophagogastroduodenoscopy (EGD) to assess for malignancy, which was negative. An exploratory laparotomy was performed along with the resection of an ileocolic mass. Pathology confirmed mucinous adenocarcinoma with signet-ring cell differentiation. The patient was started on FOLFOX regimen. She is currently on her third cycle of chemotherapy and doing well with an aim to cure. DISCUSSION: The aforementioned case illuminated the diagnostic challenge of signet-cell adenocarcinoma of the ileum. This case report is important because it highlights the importance of considering malignancy in the differential diagnosis when newly diagnosed inflammatory bowel disease does not respond to treatment. Despite its rarity, clinicians should maintain a suspicion of SRCC in the absence of histological confirmation.Figure 1.: Tubulovillous adenoma. Cecal polyp showing finger-like projections formed by fibrovascular cores and lined by dysplastic epithelium. Invasive carcinoma is noted identified (H&E stain, 20x).Figure 2.: Invasive signet ring cell carcinoma of the colon with extracellular mucin pools. The tumor is seen invading the muscularis propria (arrow). A ruptured abscess is noted within the muscularis next to the invasive carcinoma (arrowhead) (H&E stain, 20x).Figure 3.: Invasive carcinoma showing signet ring cell morphology, at higher magnifications (H&E stain, Figure D: 400x).