A 14-year-old female with Turner syndrome (karyotype 45,X) had a history of abdominal pain with distention, constipation, and fever. She was first operated on for the suspicion of appendicitis, failed to improve, and was later hospitalized for further investigation and treatment. Studies demonstrated an obstructing tumor of the transverse colon, and an emergency laparotomy was performed. The final diagnosis was a signet-ring cell carcinoma of the colon with diffuse peritoneal dissemination and metastasis to paracolic lymph nodes. On the basis of this case, we report the association of Turner syndrome with malignancies and also some aspects of colon cancer in childhood.