Malignant transformation occurring in mature cystic teratomas of the ovary

Two cases in which tumours of contrasting malignant potential arose in mature cystic teratomas (dermoid cysts) of the ovary are presented: one patient had a spindle-cell sarcoma and the other a trabecular carcinoid. The first patient's clinical course was characterized by rapid recurrence of the tumour and death 3 months after surgery. The second patient is alive and well with no evidence of residual carcinoid, although the follow-up time is short. Since the surgical procedure of choice differs substantially if malignant transformation occurs in an ovarian dermoid cyst, the pathologist should be consulted intraoperatively in selected cases.