Diagnostic concordance in cases of appendiceal mucinous neoplasia referred to a tertiary referral centre.

Accurate diagnosis of appendiceal tumours and any associated peritoneal disease is clinically important but can be difficult. We retrieved the records of patients referred to the Peritoneal Malignancy Institute, Basingstoke, in the years 2016, 2017 and 2018 with a diagnosis of mucinous appendiceal neoplasia and identified 323 patients in which slides were reviewed as part of the referral pathway. Comparing the local report from the referring centre with the central review report, in 57 (18%) we identified a discrepancy. In 39 (12%) the discrepancy was in overall diagnosis, including 22 (7%) in which the local diagnosis was low-grade appendiceal mucinous neoplasm whereas the review diagnosis was reactive mucosal changes, usually due to ruptured diverticulum, with no evidence of neoplasia. Our findings support the practice of central review of histopathology slides by experienced pathologists at tertiary referral centres. They also suggest that improvements in diagnostic criteria are needed.