S2135 Submucosal Myxoma: The Unusual and Unwanted Tumor Inside the Colon

Abstract

Introduction: Myxomas are benign mesenchymal neoplasms of unknown etiology and those involving the gastrointestinal (GI) tract are extremely rare. We are presenting an interesting case of myxomas in the GI tract, specifically of a polypoid colonic mucosal myxoma. Mucosal colonic myxoma represents a newly identified mesenchymal polyp of the colon and pathologists and gastroenterologists should be aware of this diagnostic entity. Case Description/Methods: A 60-year-old female with a past medical history of hypothyroidism, hyperlipidemia, gout, anxiety, CKD, and tubular adenomas, presents to the endoscopy unit after being referred for an EMR resection. During the procedure, a large 1.8 cm subpedunculated polyp in the proximal transverse colon is identified via previously placed tattoo. The polyp undergoes Submucosal injection ‘Orise’ to lift the lesion. After successful lifting, a 27mm stiff snare was used to perform the hot snare resection. A hemoclip was placed to close the defect. The specimen/resected lesion was then removed via roth net. Microscopic examination performed shows a polypoid colonic mucosa with a tubulovillous proliferation lined by adenomatous epithelium. In the submucosa there is a collection of myxoid stroma with interspersed blood vessels, collagen fragments, and rare spindle cells. The spindle cells are positive for CD34 immunostain and negative for smooth muscle actin, S100, and CD117 immunostains. Alcian blue stain highlights the myxoid stroma. Patient was stable and discharged after having a successful procedure (Figure). Discussion: Myxoma is originated from mesenchymal tissue and is characterized by the loose textured slimy tissue ofstellate cells, reticulin fibers, and mucoid substance. It is mainly found in the skin, soft tissue, and heart. Tumors that originate from the submucosa tend to protrude into the intestinal lumen as pedunculated masses. Our patient was found to have a polypoid colonic mucosa with a tubulovillous proliferation lined by adenomatous epithelium. Submucosal colonic myxoma represents a newly identified mesenchymal polyp of the colon and pathologists and gastroenterologists should be aware of this diagnostic entity.Figure 1.: Large 1.8 cm subpedunculated polyp in the proximal transverse colon identified via previously placed tattoo. Submucosal injection of 'Orise'; was performed to lift the lesion .