Low-grade mucinous neoplasm arising in a completely isolated duplication cyst of the abdominal wall: a unique case report.

Intestinal duplication cysts (IDCs) are rare congenital anomalies, most commonly arising in the small intestine. A particularly uncommon subtype, completely isolated duplication cysts (CIDCs), has an independent blood supply and lacks communication with the native bowel. Although IDCs are typically benign, malignant transformation-including low-grade mucinous neoplasms (LGMNs)-has been reported only rarely. A Caucasian male with a history of infant colostomy for ileus, later reversed, presented with an abdominal wall mass at the former stoma site. Imaging demonstrated a well-encapsulated cystic lesion originating above the posterior rectus sheath, and complete surgical excision was achieved uneventfully. Histopathology revealed a mucin-secreting epithelial lining with low-grade dysplasia, consistent with LGMN, with immunohistochemistry excluding alternative gastrointestinal neoplasms. The patient recovered without complications and showed no recurrence on follow-up. This represents the first documented CIDC with LGMN in the abdominal wall, highlighting the importance of early identification and surgical management.