A case report of a duodenal adenocarcinoma: a complication with Crohn's disease

The prevalence of Crohn's disease (CD) in Japan is increasing, and so is the incidence of colorectal and small bowel cancers associated with CD. However, few reports have described the malignant transformation of duodenal lesions; moreover, such a diagnosis is rarely possible preoperatively. We present a case of malignant degeneration in the duodenal mucosa associated with CD. A 54-year-old man had been receiving treatment for CD for more than 20 years. Seven years ago, he was diagnosed with duodenal stenosis related to CD. He was asymptomatic, and biopsy results from the proximal stricture showed inflammatory changes without malignant transformation. The lesion was then monitored during follow-up. In 2013, he underwent an endoscopy, which revealed an ulcerated, nodular mucosa, immediately proximal to a high-grade obstruction of the descending duodenum. A biopsy of the ulcer lesion confirmed a diagnosis of adenocarcinoma. The patient then underwent duodenopancreatectomy. Histopathological results from the resected duodenum confirmed a poorly differentiated adenocarcinoma that had invaded the subserosa. The patient recovered, and no recurrence has been observed. Although the duodenum can be accessed without difficulty during endoscopy, it is challenging to preoperatively diagnose malignant transformation. There are only four reported cases of duodenal cancer stemming from CD-associated stricture, and only one of them received a preoperative diagnosis of malignancy based on endoscopic biopsy results. Progressive duodenal narrowing and ulceration in patients with CD should indicate a need for careful endoscopic evaluation and biopsy in order to exclude malignant degeneration of Crohn's duodenitis. Early diagnosis of cases of CD-associated cancers is necessary. We report the features of a rare and illustrative case of duodenal adenocarcinoma in a patient with CD.