A practical guide for evaluating gonadal germ cell tumor predisposition in differences of sex development

Differences of Sex Development (DSD) includes a wide spectrum of etiologies and phenotypes. A subset of individuals with DSDs are predisposed to gonadal germ cell tumor (GCT). In this setting, GCT risk varies widely, depending on the DSD molecular etiology and penetrance. Prognostication based on molecular diagnosis remains challenging, as natural history data specific to recently identified molecular causes of DSD is lacking. In this review, we provide a framework for the clinical geneticist to consider GCT tumor risk in the patient with DSD. We discuss germ cell development and etiology of GCT growth, along with parameters to consider when recommending prophylactic gonadectomy including fertility, hormonal output, and malignant GTC treatment outcomes. Shortly after the 2006 reorganization of DSD nomenclature, literature reviews of natural history publications stratified GCT risk by a chromosomal, pathological, and hormonal taxonomy. Our 2017 literature review reveals a larger body of publications. However, the broad DSD GCT risk stratification within the 2006 taxonomy remains stable. We discuss precise GCT risk assessment for specific diagnoses, including androgen insensitivity, Smith-Lemli-Opitz, and 46,XY with MAP3K1 mutations and gonadal dysgenesis, as examples. We also examine the GCT risk in non-DSD syndromes, in addition to the cancer risks in DSD patients with dimorphic gonads and genitalia. This review is intended to provide a nuanced assessment of relative germ cell tumor risk in the DSD patient, including modern precise molecular diagnosis, for use by the clinical geneticist.