Abstract
A 69-year-old female was admitted to our hospital because of polyneuropathy. After the admission, dementia appeared and progressed rapidly and MR scan (T2WI) shows hyperintensity in the bil. medial temporal lobes. Paraneoplastic limbic encephalitis and carcinomatous polyneuropathy were suspected. Colonoscopy revealed a 5.5×7cm ulcerating neoplasms with elevated edges in the rectum. Abdominoperineal resection was performed. The histological diagnosis was undifferentiated carcinoma. The primary lesion of small cell carcinoma is commonly in the lung. Undifferentiated carcinoma of the colon with paraneoplastic limbic encephalitis and carcinomatous polyneuropathy was thought very rare.
