[A case report of undifferentiated carcinoma of the sigmoid colon with rhabdoid features].

A 45-year-old woman with persistent abdominal pain was admitted to our hospital. Detailed examination revealed a type 4 lesion with circumferential narrowing, which was diagnosed as a poorly differentiated carcinoma following forceps biopsy and ascitic fluid cytology. Although the lesion was surgically resected, the ascites increased rapidly, and her general condition deteriorated in the postoperative period. She died 6 weeks after the appearance of her symptoms. Autopsy and histological examination confirmed a very rare undifferentiated colon carcinoma with rhabdoid features, which is a high-grade malignant lesion associated with a poor prognosis.