Rare Colonic Schwann Cell Hamartoma Found on Repeat Screening Colonoscopy: Case Presentation

Abstract

Introduction: A 60-year-old Caucasian male who had two previous colonoscopies done for screening purposes came in for repeat screening 7 years after his last colonoscopy and was found to have 4mm sessile distal transverse polyp comprising of mucosal Schwann cell hamartoma (MSCH). Case Description: Patient has a history of hyperlipidemia, eczema, depression, ocular migraines in form of flashing lights, work related hearing loss, diverticulosis, hemorrhoids. He has no family history of familial adenomatous polyposis, multiple endocrine neoplasia (MEN) 1 or 2, Neurofibromatosis type 1 (NF1) or Cowden syndrome. Previous colonoscopies done at year 50 showed 4mm polyp at sigmoid colon consisting of tubular adenoma. His then repeat after 4 years showed 3mm hyperplastic polyp at rectum. During current colonoscopy two polyps were found with one at distal transverse colon measuring 4mm (Fig 1) and other measuring 2.5mm sessile hyperplastic at the recto-sigmoid junction. The H&E (Fig 2) stain showed many spindle cells in the lamina propria with elongated nuclei. S-100 stain (Fig 3) was diffusely positive while epithelial membrane antigen (EMA) was negative supporting the diagnosis of MSCH. Because the spindle cells were diffusely positive for S-100 and along with no other family or personal history of syndromic conditions, testing for CD117 (KIT), CD34, GIST, RET or NF1 gene was not performed. Discussion:These MSCH are very rare and literature review showed only 10 cases have been reported till 2016 since it was fist described in 2009. Most of these cases were incidentally found during routine colonoscopies. The differential diagnosis of a neural mesenchymal colorectal polyp could be neurofibroma associated with NF 1, mucosal neuroma associated with MEN 2B, ganglioneuroma associated with Cowden syndrome, gastrointestinal stromal tumor (GIST), mucosal Schwannoma, MSCH etc. MSCH are sporadic polypoid lesions that are not associated with any syndromic conditions mentioned above so far. MSCH is usually diagnosis of exclusion as these lesions consist of Schwann cells with diffuse positivity for S-100 stain without any other cells such as fibroblast, perineural cells and axons. Without any known association with inherited disorders and with less known about its long-term behavior, researchers and clinician should be aware of this diagnosis and report of any new findings or associations. Patient was counselled to return in 5 years for a repeat screening colonoscopy.FigureFigureFigure