Mucosal Schwann-Cell Hamartoma Diagnosed by Using an Endoscopic Snare Polypectomy
A 41-year-old woman was admitted to St. Paul's Hospital for a polypectomy of a colon polyp that had been detected by chance during colonoscopy for a routine check-up. She did not have any medical history of chronic diseases, including hypertension, diabetes, hepatitis, tuberculosis, and others. She had no history of alcohol consumption, smoking or medications. Her family history did not show any NF1 or gastrointestinal malignancies. Physical examination of the head, neck, lungs, heart, skin and other systems did not reveal any significant findings. She had normal bowel sound with neither abdominal tenderness nor any palpated abdominal mass. No freckles in the armpit or inguinal areas and no specific bone lesions were observed. Peripheral blood smear examination revealed a leukocyte count of 5,900/mm3, a hemoglobin level of 11.1 g/dL, and a platelet count of 236,000/mm3. The result of coagulation was normal. A serum biochemical test revealed a total protein level of 6.8 g/dL, an albumin level of 4.4 g/dL, an aspartate aminotransferase level of 14 IU/L, an alkaline aminotransferase level of 9 IU/L, a total bilirubin level of 0.7 mg/dL, a blood urea nitrogen level of 14 mg/dL, and creatine level of 0.7 mg/dL. On colonoscopic examination, a 0.8-cm polyp with no erosion nor ulceration was found in the descending colon and was removed using a loop snare technique (). Histologically, the polyp contained a diffuse proliferation of spindle cells in the colonic mucosa, located in the lamina propria that entrapped the colonic crypts, and all cells were spindle shaped with elongated, tapering nuclei, abundant dense eosinophilic cytoplasm with indistinct cell borders, and no nuclear atypia, pleomorphism or mitoses (). By immunohistochemistry, the lesions showed strong positivity for the S-100 protein and no activity for CD34, CD117 or for smooth muscle actin ().\nThe polyp was composed of pure fusiform Schwann cells. It was different from a neurofibroma of NF1, which shows a heterogeneous cellular composition, including Schwann cells, fibroblasts, perineural-like cells, and axons. Considering the histological findings, the immunohistochemical panel, and the absence of associated inherited syndromes, we diagnosed the polyp as a mucosal Schwann-cell hamartoma.