The pathology archives of 3 institutions were searched to identify appendectomy specimens containing LAMNs and appendiceal adenomas that were diagnosed between January 1990 and March 2014.
The benefit of further surgery to achieve a clear margin for appendiceal adenomas and LAMNs in patients who otherwise would not require surgery is less clear, although several groups recommend this practice.
There are no clear guidelines regarding appropriate management of patients with appendiceal adenomas or LAMNs who have positive surgical margins on their appendectomy specimens, particularly when the tumors are confined within the serosa.
We conclude that in patients with LAMNs confined to the appendix, without extrusion of mucin or mucinous neoplasia beyond the appendiceal serosa, involvement of the appendectomy margin by either neoplastic epithelium or acellular mucin is not associated with disease recurrence or peritoneal dissemination.
Six out of 8 LAMNs contained both KRAS and GNAS mutations.
We found that KRAS and GNAS mutations were the most common alterations identified in patients with LAMNs and low-grade/well-differentiated mucinous adenocarcinoma with PMP.
In 2013, Nishikawa and colleagues identified GNAS mutations as common in LAMNs and suggested that mutant GNAS might play a direct role in mucin production (16).
Comparison of Various Classification Systems for Low-Grade Appendiceal Mucinous Tumors Pai and Characteristics Carr and Sobin (8) Longacre (10) Confined to the Adenoma Adenoma appendix Various alterations Uncertain malignant Uncertain malignant of the muscu- laris potential potential mucosae or wall Associated with Adenocarcinoma Low malignant pseudomyxoma potential peritonei Destructive Adenocarcinoma Invasive invasion of the adenocarcinoma appendiceal wall Characteristics Misdraji et al (11) Confined to the LAMN (a) appendix Various alterations LAMN (a) of the muscu- laris mucosae or wall Associated with LAMN with peritoneal pseudomyxoma spreada peritonei Destructive Invasive adenocar invasion of the appendiceal wall Abbreviation: LAMN, low-grade appendiceal mucinous neoplasm.
17-19) In some instances, the appendix was not removed because it was felt to be normal by the surgeon,17 although appendices with LAMNs may appear grossly unremarkable.