A malignant neoplasm involving the vermiform appendix. The disease is MONDO_0001235 (appendix cancer). Also known as: cancer of the appendix, cancer of vermiform appendix, malignant appendix neoplasm, malignant appendix tumor, malignant appendix tumour, malignant neoplasm of appendix, malignant neoplasm of appendix vermiformis, malignant neoplasm of the appendix.