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Pathological terminology

Unfortunately, medical terms can sometimes be confusing and there are often multiple names for the same condition. Pseudomyxoma peritonei (PMP) is no exception and has been classified in different ways over the years. The current classification, endorsed by the World Health Organization (WHO), is shown in the Table. It uses the term “mucinous carcinoma peritonei”, which is the same as “PMP”.

Category WHO grade Typical histological features
1 Low-grade mucinous carcinoma peritonei G1 Strips of mucinous cells showing relatively few abnormal features lying within abundant mucin
2 High-grade mucinous carcinoma peritonei G2 High-grade features, involving at least 10% of the tumour
3 High-grade mucinous carcinoma peritonei with signet ring cells G3 Signet ring cells present (signet ring cells are a type of cell associated with worse prognosis)
A signet ring cell, part of the pathological terminology of PMP

Acellular mucin can occur in PMP, but also in ruptured ovarian cysts, causing it to accumulate in the peritoneal cavity. However, removing the ovarian cyst cures it. A hallmark is acellular mucin in the peritoneal cavity without epithelial cells. It is not graded.

A crash course in medical terms

If you are not familiar with the words used by doctors when describing tumours, here are some definitions:

  • benign
    Cannot spread to distant parts of the body
  • malignant
    Can spread to distant parts of the body
  • tumour
    A mass due to autonomous growth of cells, whether benign or malignant
  • neoplasm
    Another word for tumour
  • cancer
    A malignant tumour
  • lesion
    Anything abnormal on or in the body, not just neoplasms

Neoplasms are classified according the type of normal cell they resemble. For example, adenocarcinoma is a type of cancer resembling glands (adeno = gland and carcinoma = cancer of lining cells). Tumours are called mucinous if more than 50% of the mass consists of mucin.

What do you call that?

You may hear lots of terms, unfamiliar words which are difficult to remember. There is so much to take in and you won’t always have time to think to ask the right question. Our glossary is a place where you can look up exactly what something means.


The pathology of pseudomyxoma peritonei and appendix tumours

Pseudomyxoma Survivor and N Carr, MB BS FRCPath FRCPA FAcadMEd, Pseudomyxoma Survivor website, 2023

A Consensus for Classification and Pathologic Reporting of Pseudomyxoma Peritonei and Associated Appendiceal Neoplasia

Carr, Norman J. FRCPath; Cecil, Thomas D. MD; Mohamed, Faheez; Sobin, Leslie H.; Sugarbaker, Paul H.; González-Moreno, Santiago MD PhD; Taflampas, Panos MD; Chapman, Sara PhD; Moran, Brendan J. MD, A Consensus for Classification and Pathologic Reporting of Pseudomyxoma Peritonei and Associated Appendiceal Neoplasia, The American Journal of Surgical Pathology: January 2016 – Volume 40 – Issue 1 – p 14-26 doi: 10.1097/PAS.0000000000000535

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Complete cytoreduction for pseudomyxoma peritonei (Sugarbaker technique)

National Institute for Health and Care Excellence (NICE) Complete cytoreduction for pseudomyxoma peritonei (Sugarbaker technique), April 2004 [Online]. Available https://www.nice.org.uk/Guidance/ipg56 [Accessed February 2018]. Under review February 2018.