MicroRNAs and Recent Insights into Pediatric Ovarian Cancers | Frontiers in Pediatric Oncology

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Introduction

Adnexal masses are a common cause for the medical evaluation of young women and girls. Approximately 5–10% of all women in the United States undergo surgery for an adnexal mass at some point in their lives (Barakat et al., 2009). In most cases, adnexal masses in young women are benign cystadenomas that arise either from the ovary or developmental remnants of paratubal tissue. However, 2–8% pediatric adnexal masses are ultimately diagnosed as cancer (Barakat et al., 2009).

Clinical Spectrum

In contrast to adult ovarian cancers, pediatric ovarian cancers typically originate in germ cells or stroma rather than epithelia lining the ovarian surface, distal fallopian tube, or peritoneal implants of endometriosis. Approximately 40% of ovarian tumors are germ cell tumors whereas 25% are sex cord-stromal tumors (Barakat et al., 2009). Germ cell ovarian cancers are a diverse category of tumors that include both benign and malignant disease. Ovarian teratomas (“dermoids”) are the most common and perhaps best-known example of a benign ovarian germ cell tumor. While their true incidence in the general population is unknown, dermoids account for approximately 65% of adnexal masses in pediatric patients presenting for treatment (Ehren et al., 1984). Malignant ovarian germ cell tumors are much less common than their benign counterparts. Histologically, malignant germ cell tumors recapitulate rudimentary tissues observed during normal human development (Table 1). The most common malignant ovarian germ cell tumor is dysgerminoma (Chieffi et al., 2012). Other germ cell tumors observed in the ovary include immature teratomas and endodermal sinus tumors. Combinations of different histologic elements are frequently observed in the same ovarian tumor. These “mixed” tumors frequently contain elements of dysgerminoma (Chieffi et al., 2012)......