1473 A Vanishing Cecal Mass

Abstract

INTRODUCTION: Systemic mastocytosis (SM) is a rare disease characterized by infiltration of mast cells in extracutaneous organs. Although gastrointestinal (GI) manifestations such as nausea, vomiting, abdominal pain are observed in up to 60-80% of patients, colon lesions are rarely identified. Here we describe an unusual case of SM that manifested as a colon mass on routine screening colonoscopy. CASE DESCRIPTION/METHODS: A 71-year-old, asymptomatic, female with a long history of urticaria pigmentosa was referred to a gastroenterology clinic for evaluation of an eight by twelve centimeter, polypoid mass involving the cecum and ileocecal valve, found on screening colonoscopy. Subsequently, a CT scan noted mucosal hyperenhancement with slight vascular engorgement and colonic wall thickening involving the cecum and proximal ascending colon. Pathology from the initial biopsies revealed dense (>100 per high powered field) infiltration of mast cells that stained positive for CD117 and CD25 cell surface proteins. The initial, large, polypoid, cecal mass was not present on repeat colonoscopy with upper endoscopy. Instead, there was patchy nodular- appearing mucosa in the right colon. Follow-up biopsies of the upper and lower GI tract revealed dense infiltration of mast cells in the duodenum, ileum, ascending colon and transverse colon as well as elevated serum tryptase level (38 ug/L), all findings consistent with GI involvement of SM. Histamine-blocking therapy with ranitidine and cetirizine was commenced. DISCUSSION: Systemic mastocytosis results from a sporadic somatic mutation in the KIT gene that encodes a protein implicated in cell growth, division & survival that results in overproduction of mast cells that accumulate in organs. There are four subtypes of SM that range in severity from slow and indolent to rapidly progressive towards organ failure. It is important to recognize and categorize systemic involvement of mastocytosis to aid in prognosis and treatment. Frequently, GI symptoms are mild but can include more serious effects of mast cell infiltration including peptic ulcer disease, malabsorption and non-cirrhotic portal hypertension. Specifically important to gastroenterologists is the recognition of GI involvement of mastocytosis disorders and understanding of appropriate evaluation, including upper and lower endoscopy with random biopsies to identify mast cell infiltration. Although GI symptoms are frequent and result in endoscopic evaluation, there are only rare reports of colon masses.