High-grade appendiceal mucinous neoplasms

High-grade appendiceal mucinous neoplasms (HAMN) are rare mucinous tumours of the appendix showing high-grade cytologic atypia, c.f. low-grade appendiceal mucinous neoplasms (LAMN). The distinction between both LAMN and HAMN is done on a histologic ground and those tumours basically look the same on imaging. Please, refer to the LAMN article for a detailed conjoined discussion on their imaging findings. 

Terminology 

Considerable controversy still exists on mucinous neoplasms of the appendix pathologic classification and nomenclature 3. According to a panel of specialist review in 2016, a new nomenclature and classification for the appendiceal mucinous neoplasms based on their histologic type and biologic behaviour has been proposed, which now includes the “high-grade appendiceal mucinous neoplasm”. The HAMN was proposed to include the lesions that have high-grade atypia and thus cannot be grouped as an LAMN, but also do not have the infiltrative invasion to be characterised as an appendiceal mucinous adenocarcinoma 1-2.

Pathology

Histologically these tumours show high-grade cytologic atypia associated with at least one of the following 1-2

  • loss of the muscularis mucosae 
  • fibrosis of the submucosa
  • rupture of the appendix
  • mucin and/or tumoral cells outside the appendix
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Article information

rID: 54956
Section: Pathology
Synonyms or Alternate Spellings:

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