Intra-abdominal desmoid tumor on the background of lynch syndrome. An unusual association mimicking recurrent colon cancer (FULL ARTICLE)

Summary

A 46-year-old gentleman was referred to our institution with a 6-month history of recurrent rectal bleeding. He had a strong family history of cancer with two brothers having died of colon cancer before the age of 50, and a son of brain tumor at the age of 2. Colonoscopy showed a large hypervascular pedunculated polyp (2x2.5 cm) in the sigmoid colon that was excised. Follow-up colonoscopy a year later, showed no recurrence at the polypectomy site, but another sessile 2x1 cm polyp was found and excised in the ascending colon. A laparoscopic right hemicolectomy with primary side-to-side ileo-transverse anastomosis was performed. Genetic testing confirmed the diagnosis of Hereditary Nonpolyposis Colorectal Cancer (HNPCC-Lynch syndrome). A follow-up CT scan of the abdomen and pelvis showed a speculated mesenteric mass of 2x1.7 cm in close proximity to the ileocolic anastomosis. A PET-CT scan was performed, and this showed the mass to have FDG uptake with SUV max of 4.67 (Mean Liver SUV based on body weight was 2.6). Findings were suggestive of local recurrence and an exploratory laparotomy was carried out. Histopathology showed no malignancy, but an ill-defined spindle cell proliferation within the pericolic fat, and mesentery arranged in short sweeping fascicles with long thin-walled blood vessels. Tumor cells were positive for beta catenin and negative for SMA, desmin and CD117, confirming the diagnosis of desmoid tumor and excluding other differential diagnoses of GIST, leiomyoma, neurofibroma and schwannoma. Two years’ surveillance workup showed no evidence of recurrence.