Heterotopic Cutaneous Adnexa Arising from the Ascending Colon Presenting as a Chronic Abdominal Wall Sinus: A Rare Congenital Anomaly and Diagnostic Challenge

A chronic abdominal wall sinus tract caused by heterotopic cutaneous adnexa arising from the colonic serosa is extremely rare and readily misdiagnosed. We report a 39-year-old woman with congenital scoliosis and a 30-year history of intermittent, odorless, non-feculent discharge from a cutaneous opening in the right lower abdominal wall; she had no prior abdominal surgery. Contrast-enhanced computed tomography (CT) revealed a non-enhancing sinus tract extending from the ascending colon toward the abdominal wall, whereas colonoscopy showed normal colonic mucosa with no fistulous communication. Laparoscopic exploration revealed a tubular structure arising from the serosal surface of the middle ascending colon that bifurcated into an abdominal wall branch and a pelvic branch, the latter not identified on preoperative imaging. Because the lesion was considered benign but preoperative imaging could not determine the depth of involvement, and an unexpected pelvic branch was found intraoperatively, a laparoscopic limited right hemicolectomy was performed with en bloc excision of both branches. Histopathological examination confirmed the absence of intestinal epithelial components, and immunohistochemistry was positive for cytokeratin 7 (CK7), GATA-binding protein 3 (GATA-3), and p63, confirming a cutaneous adnexal origin. The patient recovered uneventfully, with no recurrence at the 6-month follow-up. This case may represent a rare congenital developmental anomaly related to abnormal persistence of ectodermal components during embryologic development; however, definitive embryologic proof is lacking. It emphasizes the importance of a detailed history, the inclusion of congenital heterotopic cutaneous adnexal lesions in the differential diagnosis of refractory abdominal wall sinus tracts, and complete excision of all sinus tract branches to prevent recurrence and repeated ineffective interventions.