GPER1 and in situ carcinoma: Thus, excessive fetal exposure to xenoestrogens with high affinity for the nonclassical estrogen GPCR (e.g., GPR30), such as shown here for BPA, may stimulate abnormal nongenomic proliferation of gonocytes, consequently resulting in malignant germ cell transformation/carcinoma in situ and then testicular germ cell cancer, the most frequent cancer of young men, with increasing incidence.