Squamous cell carcinoma arising in a mature cystic teratoma invading the sigmoid colon: a rare presentation.

We discuss a rare presentation of malignant teratoma in a 63-year-old woman who was admitted to accident and emergency with abdominal distension, bloody diarrhoea and peritonitis. CT of the abdomen and pelvis showed free air in the abdomen and a gas-fluid filled cavity measuring 12×6 cm in the mid-pelvis with possible fistulation that was suspicious for malignancy. A 10×12 cm ruptured dermoid cyst was found intraoperatively, which was adherent to the bowel wall.