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Updated: Dec 9, 2025
Culture and Imaging of Ex Vivo Organotypic Pseudomyxoma Peritonei Tumor Slices from Resected Human Tumor Specimens
Published on: December 9, 2022
Macroscopic and microscopic characteristics of low grade appendiceal mucinous neoplasms (LAMN) on appendectomy
Kirsten S Hegg1, Lloyd A Mack2, Antoine Bouchard-Fortier2
1Department of Anatomic Pathology, Alberta Precision Laboratories, Calgary, Canada.
Abstract:
Low grade appendiceal mucinous neoplasm (LAMN) is the primary source of pseudomyxoma peritonei (PMP). PMP may develop after seemingly complete resection of primary tumor by appendectomy, which is unpredictable due to lack of reliable prognostic indicators. We retrospectively reviewed 154 surgically resected LAMNs to explore if any of the macroscopic and microscopic characteristics may be associated with increasing risk of PMP development. Our major findings include: (1) As compared to those without PMP, the cases that developed PMP were more frequent to have (a) smaller luminal diameter (<1 cm) and thicker wall, separate mucin aggregations, and microscopic perforation/rupture, all suggestive of luminal mucin leakage; (b) microscopic acellular mucin presenting on serosal surface and not being confined to mucosa; and (c) neoplastic epithelium dissecting outward beyond mucosa, however, with similar frequency of neoplastic cells being present in muscularis propria. (2) Involvement of neoplastic cells or/and acellular mucin at surgical margin did not necessarily lead to tumor recurrence or subsequent PMP, and clear margin did not absolutely prevent PMP development. (3) Coexisting diverticulum, resulted from neoplastic or non-neoplastic mucosa being herniated through muscle-lacking vascular hiatus of appendiceal wall, was seen in a quarter of LAMN cases, regardless of PMP. The diverticular portion of tumor involvement was often the weakest point where rupture occurred. In conclusion, proper evaluation of surgical specimens with search for mucin and neoplastic cells on serosa and for microscopic perforation, which are of prognostic significance, should be emphasized.
Insights
Low grade appendiceal mucinous neoplasm (LAMN) can lead to pseudomyxoma peritonei (PMP) unpredictably. Key indicators for PMP risk include microscopic perforation and mucin on the serosal surface.
Area of Science:
- Gastroenterology
- Surgical Pathology
- Oncology
Background:
- Low grade appendiceal mucinous neoplasm (LAMN) is the primary appendiceal tumor linked to pseudomyxoma peritonei (PMP).
- PMP development post-appendectomy for LAMN is unpredictable due to a lack of reliable prognostic indicators.
- Accurate prediction of PMP risk is crucial for patient management and surgical planning.
Purpose of the Study:
- To retrospectively analyze macroscopic and microscopic features of surgically resected LAMNs.
- To identify characteristics associated with an increased risk of developing PMP.
- To explore the prognostic significance of surgical margins and appendiceal diverticula in LAMN.
Main Methods:
- Retrospective review of 154 surgically resected LAMN cases.
- Analysis of macroscopic features including luminal diameter and wall thickness.
- Microscopic examination for mucin aggregation, perforation, serosal involvement, and neoplastic cell invasion.
Main Results:
- PMP cases showed smaller luminal diameter, thicker walls, mucin aggregations, and microscopic perforation, indicating mucin leakage.
- Microscopic acellular mucin on the serosal surface and neoplastic epithelium dissecting beyond the mucosa were more frequent in PMP cases.
- Surgical margin status (involved or clear) did not definitively predict PMP development or recurrence; appendiceal diverticula were common but not solely linked to PMP.
Conclusions:
- Microscopic perforation, mucin on the serosa, and neoplastic cells dissecting outward are significant prognostic indicators for PMP development.
- Routine evaluation of surgical specimens for these features is recommended for better risk stratification.
- Appendiceal diverticula may represent a weak point for rupture but are not exclusive predictors of PMP.
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