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low-grade appendiceal mucinous neoplasm
Wednesday 18 May 2016
LAMN / mucinous neoplasms of the appendix, LAMNs
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Images
Low-grade appendiceal mucinous neoplasm (LAMN) : Macroscopy
- https://twitter.com/CArnold_GI/status/732610506763206657
- https://twitter.com/GarroneRosana/status/675446641290289153
Low-grade appendiceal mucinous neoplasm (LAMN) : Microscopy
- https://twitter.com/GIPathologyURMC/status/770294826608783364
- https://twitter.com/CArnold_GI/status/727966347754352641
- https://twitter.com/AnAtomicPath/status/490628851232292864
Typical undulating and flattened epithelium resting on fibrous stroma in appendiceal LAMN
Synopsis
Villous or occasionally flat proliferation of mucinous epithelial cells originating from appendiceal lumen.
Lesional cells typically demonstrate abundant apical mucin with elongated nuclei and low grade nuclear atypia (LAMN); however, nuclei may appear compressed.
Often associated with atrophy of underlying lymphoid tissue, crypt loss and effacement of muscularis mucosae.
Broad dissection of mucin, epithelium or both may occur with potential involvement of extra-appendiceal surface, an important finding affecting prognosis.
Extra-appendiceal mucin incites a serosal reaction and may contain neovascularization, assisting in differentiation from benign transfer of mucin during gross examination.
Ovarian metastasis
Features in favor of metastatic LAMN
Bilaterality
pseudomyxoma peritonei
subepithelial clefts
scalloped glands
pseudomyxoma ovarii
tall cells
Differential diagnosis
HAMN : High grade appendiceal mucinous neoplasm (HAMN):
- lesion arising in appendix with high grade epithelial features in the absence of infiltrative growth
- high grade nuclei (HAMN)
- may show convoluted architecture, including micropapillary architecture or cribriform architecture
teratoma-associated mucinous tumors
See also
- appendiceal mucinous neoplasms
appendix
- appendiceal pathology / pathology of the appendix
Open references
Mucinous neoplasms of the appendix: a current comprehensive clinicopathologic and imaging review. 2013. doi : 10.1102/1470-7330.2013.0003
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3582328/