Unique Considerations in Rare Gynecologic Tumors: Gestational Trophoblastic Neoplasia, Germ Cell Tumors, and Clear Cell Ovarian Cancers

Rare cancers are usually defined as an incidence of <6/100,000 persons per year. Gynecological oncology is characterized by a paradoxical high prevalence of rare cancer subtypes, especially in ovarian tumors. Ovarian germ cell tumors, clear cell ovarian cancer and gestational trophoblastic disease encompass this set of gynecologic tumors. The WHO classification distinguishes epithelial cell tumors (85% of malignant tumors) from non-epithelial tumors, sex cord stromal tumors (8% of malignant tumors), and germ cell tumors (6% of malignant tumors). The current treatment for these tumors is similar to that for ovarian cancer but advancing quickly to incorporate targeted therapy. Gestational trophoblastic tumors are usually curable, even when widely metastatic disease is present. Ovarian clear-cell carcinoma (OCCC) remains a challenging disease characterized by intrinsic chemoresistance and distinct molecular features. A more biologically aligned treatment strategy has emerged. Continued integration of molecular selection and microenvironmental modulation will likely define the next phase of therapeutic development in OCCC. The clinical features, staging, and current treatment of each of these tumors is reviewed.