Cancer of the small intestine in patients with Crohn's disease.

Due to an increase in the number of long-term cases of Crohn's disease, the risk of combined cancer in these patients has been assessed in numerous articles. Most of these reports have involved patients with cancer of the large intestine, while cases of cancer of the small intestine combined with Crohn's disease are very rare. We experienced two cases of cancer of the small intestine combined with Crohn's disease. In both cases, the patients had suffered from Crohn's disease for over 10 years and a second operation was performed after a long period without treatment following the first operation, which had achieved a favorable outcome. In both cases of combined cancer, the patients experienced ileus; however, it was difficult to discern this from ileus due to the presence of Crohn's disease. Therefore, making a definitive diagnosis of combined cancer was not possible before surgery, and the definitive diagnosis was obtained based on an intraoperative pathological diagnosis. It is thought that tumor markers transition in a manner parallel to the progression of cancer, providing a clue for cancer diagnosis. In patients with Crohn's disease, there is a pressing need to establish a method for diagnosing cancer of the small intestine at an early stage.