Differential diagnosis of appendiceal serrated lesions and polyps and low-grade appendiceal mucinous neoplasm: analysis of 88 cases

• Published in: Journal of cancer research and clinical oncology Vol. 148; no. 7; pp. 1761 - 1769
• Main Authors: Lu, Yiyan, Qi, Changhai, Xu, Hongbin, Jin, Mulan
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-07-2022; Springer Nature B.V
• Subjects: Calcification; Cancer Research; Differential diagnosis; Fibrosis; Hematology; Immunohistochemistry; Internal Medicine; Lamina propria; Lesions; Medicine; Medicine & Public Health; Mucin; Mucosa; Oncology; Original Article – Clinical Oncology; Polyps; Tumors; Appendiceal mucinous neoplasm; Diverticulum; Appendix; Serrated lesions and polyps
• ISSN: 0171-5216; 1432-1335
• DOI: 10.1007/s00432-021-03757-6

Purpose
To identify clinicopathological features for the differential diagnosis of appendiceal serrated lesions and polyps (SPs) and low-grade appendiceal mucinous neoplasm (LAMN) for the purpose of avoiding over‐diagnosis.
Methods
Clinical data and pathological features of 66 patients with SPs diagnosed at the Aerospace Center Hospital between January 2013 and January 2021 were collected and compared to 22 cases of LAMN.
Results
SPs, compared with LAMN, are likely to be associated with acute inflammation (SPs 53.0% vs. LAMN 18.2%), and may be located in the appendix partly, although with smaller diameter (average 9.6 vs. 27.2 mm); epithelial structures of serrated (100% vs. 22.7%) and filiform villous (47.0% vs. 18.2%) were often found in SPs. SPs occasionally show attenuated or flattened morphology (16.7% vs. 100%) and undulating or scalloped (7.6% vs. 40.9%) structures, and can also be accompanied by diverticulum (18.2% vs. 18.2%) and acellular mucin in the appendiceal wall (16.7% vs. 54.5%), which causes confusion with LAMN. The key point of the differential diagnosis is to observe whether the muscularis mucosa exists (loss, 0% vs. 100%) and fibrosis of the appendiceal wall (0% vs. 100%). SMA immunohistochemistry can assist in the diagnosis. Calcification is also indicative of LAMN.
Conclusions
The epithelial structure of SPs can appear flattened and focally scalloped, and can be accompanied by mucin in the appendiceal wall, which may appear as complex lesions, easily over-diagnosed as LAMN. Key differential diagnostic features are identifying the structure of lamina propria, determining whether the muscularis mucosa exists, and whether the appendiceal wall is fibrotic.