Concurrent presentation of appendiceal sessile serrated lesions with other appendiceal neoplasms

Sessile serrated lesions (SSL) of the appendix are rare appendiceal neoplasms, often identified incidentally on appendix resection and only rarely discovered prior to surgery. This study aims to better characterize appendiceal SSL and their relation to other appendiceal neoplasms.

The anatomic pathology database was reviewed for all cases in which the appendix was resected from 2015 to 2023. Cases with a diagnosis of appendiceal sessile serrated lesion were included in the study. Indications for resection and available molecular testing were identified through the electronic medical record.

A total of 103 cases of appendiceal SSL were identified. The majority of resections were performed for non-neoplastic indications, either for acute appendicitis or incidentally during a different surgical procedure. SSL was most commonly seen concurrently with low-grade appendiceal mucinous neoplasm, high-grade appendiceal mucinous neoplasm, and primary appendiceal adenocarcinoma, co-presenting in 15, 4, and 12 cases respectively. Molecular data was available for a small subset of cases co-presenting with cancer, with KRAS and GNAS being the most commonly mutated genes.

We demonstrate that appendiceal SSL can be seen in conjunction with other appendiceal neoplasms, predominantly appendiceal mucinous neoplasms and primary appendiceal adenocarcinoma. Appendiceal mucinous neoplasia or adenocarcinoma typically presents at a high clinical stage when present concurrently with SSL. Similar to other studies, appendiceal SSL are most commonly an incidental diagnosis, typically in the context of appendectomy for acute appendicitis.