Standardization of the pathologic diagnosis of appendiceal mucinous neoplasms

Abstract

Although the understanding of appendiceal mucinous neoplasms (AMNs) and their relationship with disseminated peritoneal mucinous disease have advanced, the diagnosis, classification, and treatment of AMNs are still confusing for pathologists and clinicians. The Gastrointestinal Pathology Study Group of the Korean Society of Pathologists (GPSG-KSP) proposed a multicenter study and held a workshop for the “Standardization of the Pathologic Diagnosis of the Appendiceal Mucinous Neoplasm” to overcome the controversy and potential conflicts. The present article is focused on the diagnostic criteria, terminologies, tumor grading, pathologic staging, biologic behavior, treatment, and prognosis of AMNs and disseminated peritoneal mucinous disease. In addition, GPSG-KSP proposes a checklist of standard data elements of appendiceal epithelial neoplasms to standardize pathologic diagnosis. We hope the present article will provide pathologists with updated knowledge on how to handle and diagnose AMNs and disseminated peritoneal mucinous disease.

Unearthing novel fusions as therapeutic targets in solid tumors using targeted RNA sequencing

“…However, certain tumors such as undifferentiated pleomorphic sarcoma are histopathologically ambiguous, meaning that they cannot be specifically diagnosed even after considering all available pathological approaches. To avoid this ambiguity, new standards have been established and applied for pathological diagnosis ( 30 ). However, diagnostic confusion still arises among pathologists and clinicians, and such instances are referred to as ‘undifferentiated,’ ‘poorly differentiated,’ ‘uncertain,’ or ‘undefined.’ In such cases, patients may be excluded from receiving appropriate care because of organ-based diagnosis and treatment.…”

Delivery of an Incidental Appendiceal Mucinous Neoplasm

“…LAMNs are rare, non-invasive epithelial proliferations that exhibit an absence of infiltrative growth and account for approximately 1% of gastrointestinal neoplasms [ 1 , 2 ]. Histologically, their hallmark feature is a villous or flat proliferation of mucinous epithelium with low-grade atypia [ 2 ].…”

“…Due to the differing degrees of appendiceal wall fibrosis found in LAMN, the typical colorectal TNM staging is unsuitable [ 1 , 4 ]. pTis (in LAMNs) includes stages pTis, pT1, and pT2 of colorectal cancer.…”

“…pTis can be further stratified into either pTism, in which fibrosis is confined to the mucosa with cellular mucinous or mucinous epithelium in the inner side of the fibrotic mucosa, or pTisf, in which fibrosis extends beyond the mucosa, involving the muscular propria or the whole layer, with acellular mucinous or mucinous epithelium in the inner side of the fibrotic wall. T3 represents LAMNs showing either acellular mucin or mucinous epithelium involvement of subserosa or mesoappendix, and T4 includes subcategories T4a (penetration of the serosa) and T4b (directly invading adjacent organs or structures) [ 1 , 4 ].…”

“…The American Joint Committee on Cancer (AJCC) 8th Cancer Staging Manual defines LAMN as a mucinous neoplasm with low-grade cytology associated with the obliteration of the muscular mucosae, without overt features of invasion. The lamina propriety is frequently effaced, mucosal lymphoid tissues are decreased or absent, and pushing invasion is seen [ 1 ].…”