What happened, in summary

A 45-year-old woman had been followed for an ovarian dermoid cyst found during a routine medical examination. Over 5 years, the cyst slowly grew to about 6 cm, and a blood marker associated with squamous cell cancer began rising. She underwent removal of the left ovary and fallopian tube because doctors were concerned that the cyst might have become malignant.

The cyst looked like a typical dermoid during surgery, but final pathology showed well-differentiated invasive squamous cell carcinoma arising within the mature cystic teratoma. One month later, she returned for additional surgery that included hysterectomy and removal of the right ovary and fallopian tube. At her request, lymph node and omental surgery were not performed. No residual cancer was found in the additional surgical specimens, and the tumor was classified as Stage I.

She then received paclitaxel and carboplatin chemotherapy. At 22 months after treatment, she remained free of clinically identifiable recurrence. Her case highlights how malignant transformation can occur in a long-standing ovarian dermoid cyst even when the cyst initially appears benign and changes slowly over time.