1500 The Incidental Raised White Lesion: A Case of Indolent Mastocytosis

Abstract

INTRODUCTION: Mastocytosis results from clonal proliferation of abnormally defective mast cells. The clinical presentation of mastocytosis can be heterogeneous, ranging from indolent disease to aggressive systemic mastocytosis, which can present with syncope, recurrent flushing, diarrhea, and abdominal pain. We present a case of an asymptomatic patient presenting for surveillance colonoscopy, found to have an isolated elevated white lesion in the colon which on biopsy was mastocytosis. CASE DESCRIPTION/METHODS: A 68-year-old man with history of hypertension and hyperlipidemia presented for surveillance colonoscopy. His last colonoscopy was five years prior and revealed one small adenomatous polyp. Vital signs were within normal limits and physical examination was unremarkable. He denied symptoms of flushing, pruritus, abdominal pain, nausea or vomiting. Colonoscopy revealed an isolated white, raised area of mucosa, measuring 5 mm in diameter which was encountered at the transverse colon (Figure 1). Biopsies of this area was obtained. Pathology of the elevated white mucosal area showed marked eosinophilic infiltrate admixed with round to spindle cells that stain positive for KIT and CD25. These findings are consistent with involvement by an abnormal mast cell infiltrate. The patient's complete blood count was normal and serum tryptase level was within normal limits. Given these findings, his diagnosis was consistent with asymptomatic indolent mastocytosis. He was recommended to have yearly complete blood count, liver function tests and tryptase level, in addition to bone density screening, bone marrow biopsy and close follow up with hematology and gastroenterology. DISCUSSION: Mastocytosis results from clonal proliferation of abnormal mast cells which can accumulate in the bone marrow, skin and other organs including the gastrointestinal tract. Gastrointestinal findings on colonoscopy can include normal mucosa, raised white-colored mucosa, polypoid lesions and ulcers or erosions involving the upper or lower gastrointestinal tract. While many patients with gastrointestinal tract involvement have symptoms of abdominal pain, nausea and diarrhea, this case highlights the importance of recognizing the endoscopic manifestations of asymptomatic indolent mastocytosis.