Adenocarcinoma occurs less frequently in the small intestine than in the large intestine. Occasionally, it develops on the background of Crohn's disease, due to long-term chronic inflammation. A case of a young man with Crohn's disease who had not been treated for years is presented. The histological examination confirmed signet ring cell carcinoma in the terminal ileum. The carcinoma formed in the surroundings of a deep fissure area where dysplastic glands were confirmed, confirming the local development. The tumor also infiltrated the muscularis propria with perineural and vascular spread. Great care must be taken when processing this type of surgical preparation, and in all similar cases, the possibility of a malignant process should be considered. Macroscopically the tumor could not be clearly identified so the entire suspected area was processed. There are no specific immunophenotype to identify the small intestinal origin, however, CK7, CK20, CDX2, SATB2, EMA (MUC1), MUC5AC, MUC6, Villin reactions may be helpful. In addition to long-term chronic inflammation, other etiological factors may include ileal conduits, reservoirs, acid exposure, gluten-sensitive enteropathy, significant alcohol consumption, sugar or processed carbohydrate consumption, and smoking. In addition to curative surgical solutions, adjuvant chemo- and radiotherapy are considered as treatments. The 5-year survival rate of signet ring cell carcinoma complicated by Crohn's disease is barely 20-30%. Orv Hetil. 2025; 166(19): 744-749.