extragonadal germ cell tumor (Monarch Disease Ontology id MONDO_0018201) is a germ cell tumor arising in an anatomic site other than the testis or ovary (e.g., central nervous system, lung, mediastinum, and retroperitoneum). Also known as: extragonadal germ cell neoplasm, extragonadal germ cell neoplasms, neoplasm of extragonadal germ cell, neoplasm of the extragonadal germ cell, primary extragonadal germ cell tumor, primary extragonadal germ cell tumour, tumor of extragonadal germ cell, tumor of the extragonadal germ cell.