Gastrointestinal: Asymptomatic colonic schwannoma in an elderly woman; a rare case

Abstract

A 70-year-old woman presented following a positive fecal occult blood test. She did not have abdominal tenderness or a palpable tumor. She had no past medical history apart from hypertension and no family history of note. Her laboratory data revealed hemoglobin 12.5 g/dL, leukocyte count 5,780/mm3, CRP 0.52 mg/dL, and normal tumor marker levels. A contrast-enhanced computed tomography (CT, Figure 1) scan revealed a large, contrast-enhancing mass in her left lower abdomen. Regional lymphadenopathy was noted, but no distant metastasis was detected. Colonoscopy revealed a round, rubbery mass with an ulcerated mucosal surface in the descending colon. (Figure 2) Biopsies unfortunately provided no definite diagnosis. Contrast-enhanced CT revealed a large, solid mass, 5 cm in diameter in the descending colon. Colonoscopy revealed a large, round mass in the descending colon with a negative cushion sign. A left hemi-colectomy with regional lymphadenectomy was performed. A yellow, solid tumor with a clear margin was seen to extend to the subserosal layer (Figure 3). Microscopic and immunohistochemical examinations diagnosed the tumor as a colonic schwannoma (Antoni A and B types). Immunohistochemistry was negative for smooth muscle markers such as actin and desmin, as well as c-KIT. Positive S-100 protein staining was found (Figure 4). A hard, elastic tumor with a necrotic mucosal surface was detected on the anti-mesenteric side of the descending colon. Histology of the tumor revealed spindle-shaped cells are observed in a fascicular pattern, which was positive to S-100 protein staining and negative to c-kit staining. Colorectal schwannomas are extremely uncommon. Miettinen reported that colorectal schwannomas accounted for only 3% (20/600 cases) of all colorectal mesenchymal tumors, and only 2 such tumors were detected in the descending colon. Most schwannomas are benign but gastrointestinal tract schwannomas may occasionally undergo malignant transformation. Complete surgical resection provides the diagnosis, and in most cases, the cure. Contributed by