Monarch Disease Ontology identifier MONDO_0021498 (benign neoplasm of placenta) is a benign neoplasm that involves the placenta. Also known as: benign neoplasm of the placenta, benign placenta neoplasm, benign placenta tumor, benign placenta tumour, benign placental neoplasm, benign placental tumor, benign placental tumour, benign tumor of placenta.