Non-epithelial Ovarian Tumours

Non-epithelial ovarian tumours (NEOTs) are derived from the germ cell and non-epithelial components of the gonads, as opposed to the epithelial ovarian cancers which arise from ovarian epithelium. They represent very rare tumour entities comprising a heterogeneous group of benign or malignant tumours. There are two main groups, namely germ cell tumours and sex cord– stromal tumours (see Table 15.1). Malignant ovarian sex cord–stromal tumours comprise only 1.2% of all primary ovarian malignancies, while malignant germ cell tumours account for only about 5% of all malignant ovarian neoplasms. They usually affect younger women and thus present clinicians and patients with a therapeutic dilemma in regards to fertility-sparing options when the disease is locally advanced or metastatic.

Malignant Germ Cell Tumours

Ovarian germ cell tumours (OGCTs) primarily affect young, premenopausal women until the third decade of life, and represent approximately 70% of all ovarian neoplasms in this age group. However, germ cell tumours may also affect postmenopausal women and should be considered in the differential diagnosis in older women with suspected ovarian tumours. In most instances, no predisposing factors are found. However in rare cases some may arise from fully differentiated mature teratomas, otherwise known as dermoid cysts. Dysgerminomas are more common in phenotypic females who have a Y chromosome, such as those with gonadal dysgenesis or complete androgen insensitivity and rarely in Turner syndrome.

Pathology

OGCTs can be broadly divided into:

They are best thought of as a spectrum of disorders ranging from the pre-malignant dermoid and immature grade I/II OGCT through to the malignant immature grade III malignant germ cell tumours, dysgerminomas (equivalent to male seminomas), nondysgerminomatous and mixed forms. Since germ cells can differentiate to form all cell types seen in the neonate and adult any combination of pathologies are possible, although some are more common than others. For example, elements of yolk sac tumour, choriocarcinoma and dysgerminoma are more commonly seen than embryonal or rhabdomyosarcoma. The cellular elements present can help to predict clinical behaviour, and determine the production of tumour markers. Very rarely, cancers from a variety of other origins can have histological elements that mimic malignant germ cell tumours, including tumour marker secretion, and this can produce diagnostic dilemmas.