A 79-year-old female was referred for endoscopic evaluation after a positive fecal occult blood test. There was a long-standing history of iron deficiency anemia, weight loss with intermittent touts of intractable vomiting, and nausea. Esophagogastroduodenoscopy revealed a secondary lumen between the duodenum and transverse colon with necrotic mucosa and a blind opening. Subsequent colonoscopy revealed similar necrotic mucosa at the transverse colon and fistula formation with communication into the duodenum. Signet ring cell carcinoma (SRCC) was evident in histologic analysis. SRCC carries a poorer prognosis than other variants of colorectal carcinoma (CRC). Proposed mechanisms of increased mucin production can lead to mucosal wall destruction and have profound manifestations, such as in our patient with duodenocolic fistula.