Germ cell tumors (GCTs) are rare in childhood, representing only 3.5% of childhood cancers, but a common malignancy in adolescents and young adults (AYAs), accounting for 13.9% of neoplasms in adolescents between age 15 and 19 years. The overall outcomes of patients treated for GCTs are excellent. However, as seen in other cancers, outcomes for AYA patients are significantly worse. Understanding the reasons for this observation has led to different approaches to diagnosis, staging, and treatment. The Malignant Germ Cell International Consortium was created to bring together pediatric, gynecologic, and testicular cancer specialists to promote research initiatives and provide evidence-based approaches in the management of GCTs across different age groups. Collaboration between multiple subspecialties is essential to further understand the disease continuum, the underlying biologic characteristics, and the development of appropriate therapeutic approaches. This review focuses on the unique characteristics of patients with extracranial GCTs in the AYA group.

Over the past decade, wingless-activated (WNT) medulloblastoma has been identified as a candidate for therapy de-escalation based on excellent survival; however, a paucity of relapses has precluded additional analyses of markers of relapse. To address this gap in knowledge, an international cohort of 93 molecularly confirmed WNT MB was assembled, where 5-year progression-free survival is 0.84 (95%, 0.763–0.925) with 15 relapsed individuals identified. Maintenance chemotherapy is identified as a strong predictor of relapse, with individuals receiving high doses of cyclophosphamide or ifosphamide having only one very late molecularly confirmed relapse (p = 0.032). The anatomical location of recurrence is metastatic in 12 of 15 relapses, with 8 of 12 metastatic relapses in the lateral ventricles. Maintenance chemotherapy, specifically cumulative cyclophosphamide doses, is a significant predictor of relapse across WNT MB. Future efforts to de-escalate therapy need to carefully consider not only the radiation dose but also the chemotherapy regimen and the propensity for metastatic relapses.

The bone health of adults is dependent on the appropriate acquisition of peak bone mineral mass during late childhood and adolescence. Measurement of bone mineral density (BMD) in clinical practice is accomplished usually by dual energy x-ray absorptiometry that provides 2-dimensional (areal) values for BMD, does not distinguish cortical from trabecular bone, and should be adjusted for height and weight when used for children and adolescents. Peripheral quantitative computed tomography (pQCT) provides volumetric measures of BMD and geometry in both cortical and trabecular bone and, unlike dual energy x-ray absorptiometry, does not need adjustment for body size. Studies of bone health in young people require reference data for normative comparison. A literature review from 1946 to 2012 identified 1886 titles suggesting use of pQCT, with only 32 reporting some form of normative data. A detailed review of these 32 reports revealed a lack of consensus among users for standard scan locations in upper and lower limbs, acquisition protocols and analytical steps, and variables reported. Meaningful and effective use of pQCT for assessing bone strength and overall bone health in all age groups will require better defined normative data derived with common measuring techniques, equipment, and analytical approaches.