S3996 Signet Ring Cell Adenocarcinoma Presenting as Persistent Diarrhea and Colonic Stricture

Introduction: Signet cell adenocarcinoma (SRCC) is an extremely rare and aggressive subtype of colorectal cancer, accounting for less than 1 percent of cases. It is often misdiagnosed or overlooked because it mimics benign conditions such as colitis and inflammatory bowel disease. SRCC gets its name from the mucin accumulation in the cytoplasm of tumor cells, pushing the nucleus to the back. Spreading throughout cells without forming a distinct mass, SRCC typically responds poorly to standard treatment. This case report is about a patient with sigmoid SRCC who initially presented with persistent diarrhea and colonic stricture. Case Description/Methods: A 49-year-old man with no history of prior colonoscopy presented with 6 weeks of severe lower abdominal cramping, bloating, urgency, and watery diarrhea occurring 10 to 12 times per day. A stool PCR found that the patient was positive for Enteroaggregative, Enteropathogenic, and Enterotoxigenic strains of Escherichia coli. Even after treatment with antibiotics, his symptoms persisted. Use of computed tomography and magnetic resonance imaging indicated a 10-cm segment of thickening in the sigmoid colon without signs of lymphadenopathy. During colonoscopy, a colon stricture was found 25-cm from the anal verge causing a halt on the procedure. The biopsy of the area was inconclusive, only revealing that there was inflammation and hyperplastic development. With the severity of his continuing and worsening symptoms, and with the stricture obstruction, surgical resection was employed. Final pathology diagnosed invasive signet cell adenocarcinoma of the sigmoid colon. Discussion: SRCC is difficult to diagnose due to the subtlety and similarity of its symptoms to benign gastrointestinal conditions, making early recognition problematic. Without forming a distinct mass, it can often get missed with surface-level biopsy. The presence of a colonic stricture lacking a clearly defined mass should be a cause for concern for invasive cancers such as SRCC. With surface-level biopsy revealing inconclusive results, early surgical consultation is necessary. This case highlights the importance of considering SRCC as a diagnosis in patients presenting with persistent gastrointestinal symptoms and colonic strictures, however benign they may seem.