S2002 Colonic Schwannoma: A Cause for Nerves?

Abstract

Introduction: Schwannomas arise from schwann cells, and though they are the commonest of all peripheral nerve tumors, it is exceedingly rare for them to be detected in the lower gastrointestinal (GI) tract. Here, we present the case of a submucosal colonic schwannoma detected incidentally as part of a routine colonoscopy for colorectal cancer (CRC) screening and discuss the clinical significance of such tumors. Case Description/Methods: A 59-year-old male patient with intermittent constipation presented for colonoscopy for CRC screening. A previous colonoscopy 7 years prior had been unremarkable. Family history was notable for CRC in several second-degree relatives. The patient’s past medical history was significant for non-alcoholic fatty liver disease, well-controlled human immunodeficiency virus infection and prediabetes. Physical examination was unremarkable. At colonoscopy, an 8 mm submucosal lesion was found in the cecum. This was sessile and firm, and did not demonstrate a pillow sign characteristic of lipoma. The lesion was resected using a saline injection-lift technique and hot snare. At histology, the lesion was described as tan-pink polypoid tissue, with negative margins (Figure). Immunohistochemically, the tumor cells were diffusely and strongly positive for S100 and negative for CD117, DOG1, SMA and desmin. This was consistent with a diagnosis of schwannoma. Discussion: When GI schwannomas arise, they are most commonly found in the upper GI tract, with 60-70% of GI cases found in the stomach and only 3% in the colon. There are no clear risk factors for their development other than advanced age. As in our patient’s case, colorectal schwannomas are typically detected incidentally on screening colonoscopies. They can be asymptomatic, or present with rectal bleeding (22.9%), abdominal pain (15.6%) or constipation (7.3%). The mass effect of large schwannomas can lead to colonic obstruction necessitating surgical resection of the tumor, but smaller lesions can typically be resected endoscopically. Schwannomas present as submucosal lesions and are almost always benign, with only atypical versions harboring any malignant potential. Numerous studies have demonstrated that recurrence after complete resection is rare, even after extended follow-up. There is no established guidance regarding follow-up intervals for patients with colorectal schwannomas, owing to their rarity. Based on the lack of malignant potential and the low risk of recurrence, we recommended a repeat colonoscopy in 5 years for our patient.Figure 1.: Cecal schwannoma in macroscopic (left) and microscopic (right) views.