A benign neoplasm that involves the vermiform appendix. The disease is benign neoplasm of appendix (MONDO_0021465). Also known as: benign appendix neoplasm, benign appendix tumor, benign appendix tumour, benign neoplasm of the appendix, benign tumor of appendix, benign tumor of the appendix, benign tumour of appendix, benign tumour of the appendix.