Immature Malignant Teratomas

These are rare tumors that differ from benign teratomas in that the component tissues resemble embryonal and immature fetal tissue. The tumor is found chiefly in prepubertal adolescents and young women, the mean age being 18 years.98

Morphology. The tumors are bulky and have a smooth external surface. On section they have a solid (or predominantly solid) structure. There are areas of necrosis and hemorrhage. Hair, sebaceous material, cartilage, bone, and calcification may be present. On microscopic examination there are varying amounts of immature neuroepithelium, cartilage, bone, muscle, and others. An important risk for subsequent extra-ovarian spread is the histologic grade of tumor (I through III), which is based on the proportion of tissue containing immature neuroepithelium (Fig. 22-45).

Immature teratomas grow rapidly, frequently penetrate the capsule, and spread either locally or distantly. Stage I tumors, however, particularly those with low-grade (grade 1) histology, have an excellent prognosis. Higher grade tumors confined to the ovary are generally treated with prophylactic chemotherapy. Most recurrences develop in the first 2 years, and absence of disease beyond this period carries an excellent chance of cure.

Dysgerminoma

The dysgerminoma is best considered as the ovarian counterpart of the seminoma of the testis. Similar to the seminoma, it is composed of large vesicular cells having a clear cytoplasm, well-defined cell boundaries, and centrally placed regular nuclei. Dysgerminomas account for about 2% of all ovarian cancers yet form about half of malignant germ cell tumors. They may occur in childhood, but 75% occur in the second and third decades. Some occur in patients with gonadal dysgenesis, including pseudohermaphroditism. Most of these tumors have no endocrine function. A few produce elevated levels of chorionic gonadotropin and may have syncytiotrophoblastic giant cells on histologic examination. Like seminomas, dysgerminomas express Oct3, Oct4, and Nanog.99 These transcription factors are implicated in maintenance of pluripotency. They also express the receptor tyrosine kinase c-KIT. These proteins are useful diagnostic markers and, in the case of c-KIT, may also serve as a therapeutic target.100

Morphology. Usually unilateral (80% to 90%), most are solid tumors ranging in size from barely visible nodules to masses that virtually fill the entire abdomen. On cut surface they have a yellow-white to gray-pink appearance and are often soft and fleshy. On histologic examination the dysgerminoma cells are dispersed in sheets or cords separated by scant fibrous stroma (Fig. 22-46). As in the seminoma, the fibrous stroma is infiltrated with mature lymphocytes and occasional granulomas. On occasion, small nodules of dysgerminoma are encountered in the wall of an otherwise benign cystic teratoma; conversely, a predominantly dysgerminomatous tumor may contain a small cystic teratoma.

All dysgerminomas are malignant, but the degree of histologic atypia is variable, and only about one third are aggressive. Thus, a unilateral tumor that has not broken through the capsule and has not spread has an excellent prognosis (up to 96% cure rate) after simple salpingo-oophorectomy. These neoplasms are responsive to chemotherapy, and even those that have extended beyond the ovary can often be cured.101 Overall survival exceeds 80%.