Ileal Signet Ring Cell Carcinoma Masked by Crohn Disease.

Signet ring cell carcinoma (SRCC) is a rare, highly malignant adenocarcinoma that generally involves the stomach; ileal involvement is uncommon. Crohn disease (CD) is associated with long-standing inflammation that may predispose to small intestine adenocarcinoma. A 67-year-old male with ileal CD since age 23 years, maintained in remission by mesalamine, presented with mild intermittent attacks of abdominal cramping, an increase in bowel movements from 3 to 5 daily, and bloating for 3 months. Computed tomography enterography with contrast enhancement demonstrated 2 segments of ileal wall thickening. Colonoscopy performed 7 years prior was unremarkable. The patient received oral prednisone with mild symptomatic improvement; he declined biologics. Ileocolonoscopy 1 month later revealed a nontraversable terminal ileal stricture 15 cm from the ileocecal valve. Biopsy demonstrated signet ring cells infiltrating the lamina propria. The patient underwent laparoscopic ileocecectomy and ileocolic anastomosis. Histopathology of a 2.5-cm ileal mass showed poorly differentiated adenocarcinoma with mucin production and signet ring cell features. One metastatic mesenteric lymph node was identified. Adjuvant chemotherapy was initiated. This case of metastatic ileal SRCC occurred in the setting of long-standing, clinically controlled CD. Although the absolute risk of small-bowel adenocarcinoma in CD is low, active surveillance for small-bowel adenocarcinoma in patients with longstanding CD may be prudent, given the overlapping symptomology of SRCC and CD, the aggressiveness of SRCC, and the association of SRCC with subclinical inflammation.