Schwannoma of the colon mimicking carcinoma: a case report and literature review

Abstract

Dear Editor, Schwannomas are rare tumours, histologically deriving from the cells of Schwann, which form the neural sheath. They have been occasionally documented as primary gastrointestinal tumours most commonly occurring in the stomach. Primary schwannomas of the colon are extremely rare and their histological spectrum, clinicopathologic profile and differential diagnosis still remain controversial. Here, we highlight the problems we encountered in the diagnosis of a colonic schwannoma in a patient with intermittent subileus symptoms and we emphasise on the therapeutic options and role of radical surgery in the treatment of this rare entity. A 55-year-old man was referred to our department with a 4-months history of altered bowel habits and clinical features of large bowel obstruction (severe constipation, mild abdominal distention), which started gradually progressing over the past month. The patients’ previous medical history stated only arterial hypertension under medical treatment. The patient had initially presented to his family doctor for medical advice. A haemoccult test was positive and a colonoscopy was therefore performed. This revealed a polypoid tumour of the hepatic flexure (approximated size: 6×3 cm). Biopsies of the tumour were not diagnostic. They revealed a severe ulcerous inflammation of the colonic wall with unclear cellular atopy. A consecutive CT scan of the abdomen showed a soft tissue-like stenotic lesion of the hepatic flexure 5.0×4.3 cm in size with enlarged lymph nodes in the adjacent mesocolon. The patient was then referred to our department for further treatment. Physical findings and digital examination were not diagnostic. His appetite was stable and he reported weight loss of 5 kg over the past 2 months. Laboratory and biochemical values were in normal range. As thorough pre-operative diagnostics were highly suggestive of a malignant neoplasm, the patient was submitted to laparotomy. Intra-operative findings were consistent with those of pre-operative diagnostics. A tumour of moderately hard consistency was found in the right colonic flexure. No infiltration of adjacent structures was observed. Enlarged lymph nodes could be palpated at the transverse mesocolon along the axis of the median colic artery. As malignancy could not be ruled out, we performed an extended right hemicolectomy with ileodescendostomy in accordance to principles of surgical oncology. Surgery was performed without complications and the post-operative recovery was uneventful so that the patient was discharged after 5 days. Histology of the neoplasm showed a spindle cell tumour invading the muscularis propria and the submucosa of the right colon with ulceration of the adjacent mucosa. In the subsequent immunohistochemical examination, tumour cells showed a strong expression for the S100, a mild expression for beta-catenin and a weak expression for CD117. No expression of the smooth muscular cells for actin, CD34 and CK18 was observed. A MIB-1 growth fraction of 5% was detected. The abovementioned findings confirmed the histological diagnosis of a schwannoma of the right colonic flexure. Schwannomas, thus tumours deriving from the cells of Schwann, which form the neural sheath, are rare tumours, which pose essential diagnostic and therapeutic difficulties. Int J Colorectal Dis (2007) 22:1547–1548 DOI 10.1007/s00384-006-0264-9