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Discordant histology in pseudomyxoma peritonei

Let’s have a look at discordant histology in pseudomyxoma peritonei.

The grade of the peritoneal disease usually matches that of the appendiceal primary (the neoplasm that lead to the spread of peritoneal disease). Occasionally the grade differs (e.g. LAMN with high-grade mucinous carcinoma peritonei). This is termed “discordant histology”.

Therefore, the appendiceal primary and peritoneal disease should be graded separately and independently. It appears that prognosis is more related to the histology of the peritoneal disease.

Another example of discordance is seen when low grade PMP is found at the first operation but high grade PMP is found at a subsequent operation. Presumably, this represents progression of the disease with increasing genetic abnormalities over time.

It is a rare occurrence in pseudomyxoma peritonei, but when it does occur, it can make the diagnosis and treatment of the disease more challenging. It is important for patients with pseudomyxoma peritonei to have their tumours evaluated by a multidisciplinary team of specialists to ensure the most accurate diagnosis and personalized treatment plan. In summary, discordant grade PMP refers to peritoneal spread of a higher grade than the initial appendiceal tumour.

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References

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.