Abstract A25: Prevalence of Klinefelter syndrome among males aged 0-19 years diagnosed with germ cell tumors: A report from the Children’s Oncology Group
Authors: Williams Lindsay A. , Pankratz Nathan , Lane John , Roesler Michelle , Richardson Michaela , Frazier A. Lindsay , Amatruda James , Poynter Jenny N. 
Published: February 2019

Abstract
Previous studies have suggested that males with Klinefelter syndrome (KS; 47, XXY) may be more likely to develop germ cell tumors (GCTs), particularly mediastinal GCTs. Due to the rarity of pediatric GCTs, there are no reports characterizing the prevalence of KS among males diagnosed with GCTs.
We used data from a Children’s Oncology Group epidemiology study (2008-2015) to evaluate the prevalence of KS in males (n=433) diagnosed with GCTs (aged 0-19 years). These 433 cases provided saliva samples and had one parent who was willing to participate in the study and complete a questionnaire including questions about health history, demographics, and environmental exposures. Tumor characteristics (location and histology) were abstracted from pathology reports provided by the treating institution. GCT cases were classified as having KS if they had evidence of an extra copy of the X chromosome based on evaluation of array data from Illumina HumanCoreExome-12 genotyping chips. Genvisis was used to identify samples with sex aneuploidy and to determine the parent-of-origin for the nondisjunction. Using chi-square tests, we examined differences in age at diagnosis, race/ethnicity, tumor location and histology, and a number of birth characteristics between KS-GCT cases and GCT cases without chromosomal abnormalities (n=415). Using publically available data, we estimated the 1-year risk and corresponding Risk Ratio (RR) and 95% Confidence Interval (95% CI) of a male with KS developing a GCT.
Based on analysis of array genotyping data, 3% (n=13) of male GCT cases had KS. Among these 13 cases, the extra X chromosome was of maternal origin in 7 cases and of paternal origin in 6 cases. Of the 13 KS cases with genotyping data, 5/9 (56%) KS-GCT cases with parental questionnaire data reported receiving a diagnosis of KS. The average age at GCT diagnosis for cases with genotyping-detected KS (n=13) was 13.8 years (standard deviation [SD], 4.4 years) compared with 12.5 years (SD, 6.2 years) for GCT cases without chromosomal abnormalities (n=415; p=0.45). We did not observe significant differences in patient or birth characteristics including race, birth weight and length, maternal age, paternal age, and the use of fertility drugs between the two groups. We confirmed that KS-GCT cases were significantly more likely to be diagnosed with extragonadal tumors (GCT [n=69/411; 17%]; KS-GCT [n=11/13; 85%]; p&lt;0.01), particularly mediastinal tumors (GCT [n=20/406; 5%]; KS-GCT [9/13; 69%]; p&lt;0.01), than GCT cases without chromosomal abnormalities. Mixed/other histology was the most common histologic subtype for KS-GCT (46%) and GCTs among patients without chromosomal abnormalities (41%; p=0.60). Based on data from the CDC WONDER database and the US Census Bureau, in 2013, the risk of developing a GCT among males aged 0-19 years without KS was estimated to be 0.000014 or approximately 1 in 70,000. Using our estimate that 3% of GCTs in males aged 0-19 years are diagnosed among patients who also have KS, we estimated the risk of a GCT among males with KS to be 0.00025, or approximately 1 in 4,000 (RR: 18.8; 95% CI: 11.7, 30.0).
In our large case series of males diagnosed with GCTs, we observed that 3% of GCT cases (n=13/433) were also carriers of an extra X chromosome based on array genotyping data and were thus classified as having KS. Males aged 0-19 years with KS experience a large increase in risk of developing a GCT compared with males from the general population. Collectively, these findings suggest that young males with KS should be monitored for the development of a GCT. Similarly, the possibility of KS should be considered in males diagnosed with a mediastinal GCT during childhood or adolescence and these patients should be tested for the presence of KS.
Citation Format: Lindsay A. Williams, Nathan Pankratz, John Lane, Michelle Roesler, Michaela Richardson, A. Lindsay Frazier, James Amatruda, Jenny N. Poynter. Prevalence of Klinefelter syndrome among males aged 0-19 years diagnosed with germ cell tumors: A report from the Children’s Oncology Group [abstract]. In: Proceedings of the AACR Special Conference: Pediatric Cancer Research: From Basic Science to the Clinic; 2017 Dec 3-6; Atlanta, Georgia. Philadelphia (PA): AACR; Cancer Res 2018;78(19 Suppl):Abstract nr A25.