Summary
Primary appendiceal adenocarcinoma (APCA), goblet cell adenocarcinoma (GCA), and low/high-grade
appendiceal mucinous neoplasms (LAMN/HAMN) are distinct entities with overlapping
clinical presentation and histomorphology, leading to diagnostic challenges. We retrospectively
reviewed our archived cases between 2010 and 2018 for diagnosis reappraisal and comparative
analysis using updated terminology and modern parameters. A total of 87 cases (22
APCA, 40 GCA, and 25 LAMN pT≥3) were included. The entire cohort had 49 women and
38 men with a median age of 59.9 (range 26–88) years. There were no statistically
significant differences in age and sex among the three groups. Clinically, patients
with GCA were more likely to present with acute appendicitis (65%) and more likely
to have appendectomy as initial surgery (68%). Both APCA and GCA were more likely
to involve the proximal appendix while LAMN was more likely to involve the distal
appendix (p<0.05). All APCAs were associated with mucosal precursor lesions, most commonly tubular,
tubulovillous, or villous adenoma, flat LAMN/HAMN-pTis mucinous epithelium, or mixed,
which correlated with distinct histomorphology, tumour differentiation, and stage.
Although polypoid precursor lesions were rare in GCA, a significant proportion of
GCA showed crypt atypia associated with neoplastic cells. Immunohistochemically, APCA
had more frequent β-catenin nuclear positivity and loss of SATB2 expression (p<0.05). KRAS mutation was more common in APCA than in GCA (8/11 vs 1/7, p<0.01). We further validated the three-tiered grading system (G1, G2, G3) in GCA,
which correlated well with tumour stage and patient survival. APCA had worse progression-free
and disease-specific survivals than GCA and LAMN (pT≥3) with the latter being relatively
indolent even when perforated with peritoneal spread. Our study is the first comprehensive
comparison between all three appendiceal neoplasms. We also describe a spectrum of
previously under-recognised crypt atypia in GCA, which should trigger a diligent search
for GCA if present.
Key words
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Article info
Publication history
Published online: October 28, 2022
Accepted:
August 10,
2022
Received in revised form:
August 2,
2022
Received:
May 11,
2022
Identification
Copyright
© 2022 Royal College of Pathologists of Australasia. Published by Elsevier B.V. All rights reserved.
