testicular seminoma (MONDO_0003669, a Monarch Disease Ontology entry) is a malignant germ cell tumor arising from the testis. It is believed that it is derived from the sexually undifferentiated embryonic gonad. Treatment with radiotherapy is highly successful when the tumor is diagnosed in localized stages, which represents the majority of presentations of seminoma. Also known as: seminoma of testis, seminoma of the testis, seminoma testis, seminomatous germ cell tumor of testis, seminomatous germ cell tumour of testis, testicular seminoma (disease), testicular seminoma Pure, testicular seminomatous germ cell tumor.