LAUSR

Glomus tumor is a rare mesenchymal neoplasm originating from the modified smooth muscle cells of the glomus body. Primary colonic glomus tumor is extremely rare with only 5 cases published in the English literature. In this article, we report the sixth case of primary colonic glomus tumor in a 50-year-old female with no significant past medical history who presented with routine screening colonoscopy. The entire colon was endoscopically unremarkable except an incidental 6-mm sessile polyp located in the descending colon. Biopsy showed a densely cellular neoplasm composed of small, bland, slightly spindled to predominantly epithelioid cells with clear to eosinophilic cytoplasm arranged in nests and sheets. The tumor cells were interspersed with slit-like thin-walled vessels and scattered short nerve bundles. Immunohistochemically, the tumor cells were positive for smooth muscle actin, h-caldesmon, and CD34 (focal), but completely negative for HMB45, S100, EMA, desmin, DOG-1, and CD117. The histologic features and immunohistochemical profile supported a diagnosis of primary colonic glomus tumor. The patient was asymptomatic and disease free after the procedure.