<p>Mucinous tumours of the ovary can arise as either primary or metastatic tumours, especially from the appendix. Our study aimed to investigate the different terms used across Canada with respect to ovarian or omental involvement by an appendiceal primary tumour. Retrospective data from January 2010 to October 2022 were collected using an internal pathology database at a single centre for cases of ovarian or omental involvement by an appendiceal primary tumour. Reports were reviewed for terminology used. Subsequently a survey was sent to Canadian academic centres, asking pathologists about their use of diagnostic terminology in reporting these cases. Our study identified 39 local cases, corresponding to an average of 3.25 cases per year. A further 16 academic pathologists completed the survey. Second review by one or more pathologists was common in local cases with 62% of in-house cases being reviewed in internal consultation. All survey respondents indicated that they either sometimes (56%) or always (44%) reviewed these cases with a second pathologist. With regard to terminology, a variety of terms were used for the same pathologic process, including: “mucinous carcinomatosis ovarii”, “metastatic mucinous adenocarcinoma”, “low-grade appendiceal mucinous neoplasm (LAMN) involving the ovary”, “mucinous neoplasia”, as well as an older term, “adenomucinosis”. Our study highlights these differences, with the potential to help understand and standardize diagnostic terminology.</p>