carcinoma in situ of appendix (Monarch Disease Ontology identifier MONDO_0021290) is a in situ carcinoma that involves the vermiform appendix. Also known as: carcinoma in situ of the appendix, carcinoma in situ of vermiform appendix, stage 0 appendix cancer, stage 0 appendix carcinoma, stage 0 appendix carcinoma aJCC v7, stage 0 vermiform appendix carcinoma, vermiform appendix carcinoma in situ, vermiform appendix in situ carcinoma.