Adenocarcinoma arising in a small bowel duplication cyst

Background: Enteric duplication cysts are uncommon congenital anomalies containing a normal gastrointestinal mucosa and smooth muscle layer that can occur anywhere throughout the digestive tract. Duplication cysts have the potential for neoplastic transformation. Case report: This report describes a case of adenocarcinoma arising from a duplication cyst of small bowel, with invasion and breach of cyst wall, in a 40-year-old gentleman. A cystic lesion was found in the small bowel mesentery which had a well circumscribed smooth muscle layer beneath the layer of ulceration consisting of lymphocyte collection, macrophages and degenerating epithelial cells. A well differentiated adenocarcinoma was found within the wall of duplication cyst, invading its serosa and metastasis to mesenteric lymph node. The adjacent bowel segment submitted was having no lesion suggesting that the carcinoma had originated from the duplication cyst. Conclusion: It is difficult to diagnose a malignancy arising in a duplication cyst radiologically therefore a duplication cyst should be surgically removed completely as it carries an unpredictable risk of malignant transformation even if it is asymptomatic or apparently benign.