Immature Teratomas These neoplasms contain immature tissues (that resemble those seen in an embryo) admixed with mature (adult) elements. Immature teratomas account for only 1% of ovarian tumours but 10 - 20% of ovarian malignancies below age 20. Two-thirds have an elevated serum AFP, but the levels are much lower than in patients with yolk sac tumours. Sometimes, hCG is positive. At the time of diagnosis, approximately two-thirds have metastasized to peritoneum or nodes. They are large neoplasms with a smooth bosselated surface; capsular ruptures are seen in nearly half. The sectioned surface is predominantly solid but cysts are also present and hair is often seen. Bilaterality is rare, but there is a contralateral dermoid cyst in nearly 10%. Microscopic examination reveals a mixture of mature and immature tissues. The latter is predominantly immature neuroectoderm. A grading system is based on the amount of immature tissue present. Prognosis: Patients with Grade 1 Stage I lesions do extremely well without adjuvant therapy. With Grade 2&3 tumours, 90 - 100% have a sustained remission with contemporary chemotherapy.