1625 Colonic Schwannoma Identified in Asymptomatic Middle-Aged Female

Abstract

INTRODUCTION: Schwannomas are typically benign tumors of the neural sheath. Schwannomas of the colon are extremely rare entities; in fact, when schwannomas occur in the gastrointestinal tract, the colon is considered the least likely site. Schwannomas of the colon were previously misdiagnosed as gastrointestinal stromal tumors; however, with advances in immunohistochemical staining, the number of cases of intestinal schwannomas has gradually increased. Colorectal schwannomas can be divided into three clinicopathologic types: spindle cell, epithelioid, and plexiform. Here, we present a unique case of a colonic spindle cell schwannoma encountered in an asymptomatic patient on routine colonoscopy. CASE DESCRIPTION/METHODS: A 50-year-old female with no significant past medical history presented to gastroenterology clinic for routine colorectal cancer screening. The patient denied abdominal pain, nausea, vomiting, diarrhea, constipation, rectal bleeding, or weight loss. She also denied family history of neurofibromatosis. Physical examination was unremarkable. Laboratory studies showed that the patient had microcytic anemia (hemoglobin 10.9 g/dl, MCV 59 fL) but were otherwise unremarkable. A colonoscopy was subsequently performed and revealed a 6 mm sub-epithelial lesion in the sigmoid colon. Biopsy showed colonic mucosa with mild chronic inflammation and multiple spindle cell aggregates confined to the lamina propria (Figure 1). Cytological atypia, mitoses, and necrosis were identified in the biopsied specimen (Figure 2). Immunohistochemical assays demonstrated lack of reactivity to CD68, CD117, and DOG-1. The spindle cells were strongly positive for S100, confirming the diagnosis of mucosal Schwann cell hamartoma. DISCUSSION: Rectal bleeding, colonic obstruction, and abdominal pain are the three most common presenting symptoms for colorectal schwannoma; however, our patient denied any of these symptoms. The management of intestinal schwannomas remains controversial. Surgical resection with adequate margins remains the treatment of choice. Several sources question whether radical resection based on oncologic principles is necessary given the benign nature of these tumors. Our patient was managed conservatively with routine surveillance. Repeat colonoscopy performed approximately 3 months after the initial colonoscopy revealed no signs of recurrence or metastases. This case supports the notion that these rare mesenchymal tumors are commonly benign and aggressive therapeutic interventions are likely unnecessary.