3043 Not All Bumps Are Equal, Mucosal Schwann Cell Hamartoma a Rare Subtype

Abstract

INTRODUCTION: Benign mesenchymal polyps are an interesting group of colonic polyps. There has been a surge in the number of these polyps identified since legislation modified Medicare and began reimbursement for screening colonoscopy in patients at an average risk for colorectal carcinoma. It is important to differentiate between the different types of mesenchymal polyps given that some have correlation with hereditary diseases. CASE DESCRIPTION/METHODS: 66 year old male patient with history of hypertension presents for routine colorectal cancer screening colonoscopy. He is asymptomatic and has no family history of cancer including colon cancer. During the colonoscopy a small 5 mm polyp was found in the rectosigmoid which was removed using cold forceps polypectomy. The pathology was read as a benign mesenchymal polyp. Further staining with S-100 and CD 68 was done which revealed that this polyp was in fact a Schwann cell hamartoma. DISCUSSION: There has been 10 reported cases of mucosal schwann cell hamartoma in literature. Using immunohistochemistry for S100 highlights tissue with neural differentiation expanding the lamina propria of the colonic biopsy and CD68 highlights muciphages. These polyps resemble spindle cell proliferation and other neuronal tumors and are usually limited to the mucosa of the colon with no submucosal extension. They are usually solitary and patients do not have symptoms though a couple of cases reported finding them in the process of workup for diarrhea. Gibson and Hornick supplied the necessary name in 2009 in an attempt to differentiate it from other Schwann cell proliferation which is seen in entities like neurofibroma and ganglioneuroma. The importance of this entity is its lack of association with hereditary cancer syndromes, specifically neurofibromatosis type 1 (NF1) and multiple endocrine neoplasia 2B (RET) which is seen with neurofibromas. Also ganglioneuromatous polyposis and diffuse ganglioneuromatosis are seen in Cowden syndrome, Juvenile polyposis syndrome, MEN2B and NF1 however solitiary ganglioneuroma are not associated with hereditary diseases. It is important to differentiate this entity from others to prevent unnecessary and aggressive testing and treatment. Pathologists should include this differential as part of S 100 positive spindle cell proliferative lesions and gastroenterologists should be aware of the benign nature of this pathology.