[Mucinous tumors of the peritoneum]

Disseminated peritoneal seeding of mucin-forming tumors is a rare malignant disease with variable prognosis. Histomorphological criteria are instrumental in the prognostic assessment. The past 10 years have led to a standardization of nomenclature and subsequently to the establishment of therapeutic standards. This article aims to provide the current status of the pathological classification, staging, and grading.

Selective literature search in PubMed and Medline RESULTS: The vast majority of disseminated peritoneal mucinous diseases that correspond to the clinical presentation of pseudomyxoma peritonei (PMP) arise from mucinous tumors of the vermiform appendix. Here are to be distinguished: 1) low-grade appendiceal mucinous neoplasms (LAMN), 2) (very rare) high-grade appendiceal mucinous neoplasms (HAMN), 3) mucinous adenocarcinoma without signet ring cells (G2) and 4) mucinous adenocarcinoma with signet ring cells or signet ring cell carcinoma (G3). Other primary tumors only rarely induce PMP. Terms such as mucocele or mucinous cystadenoma of the appendix correspond to LAMN and should no longer be used. Prognostic distinctions are further made between low-grade PMP, which usually arises from LAMN, and the prognostically less favorable high-grade PMP, which usually arises from mucinous/signet ring cell adenocarcinoma or the rare HAMN. Disseminated peritoneal mucinous disease/PMP must then be further distinguished from prognostically excellent local mucin formation of the peri-appendix region.

The currently valid nomenclature, as it has emerged from consensus meetings and in parts has also found its way into the current WHO 2019, has significantly contributed to the fact that the prognosis of patients today can be better estimated and effective forms of treatment could be developed.