Moreover, we identified the ultrarare variant c.556G>A within the VCX3A gene (locus Xp22.31) in a patient with SCOS (Table 1), which is expressed exclusively in the testis (https://gtexportal.org/home/gene/ENSG00000169059.12). The gene discussed is VCX3A; the disease is small cell osteogenic sarcoma.