[A Case of High-Grade Appendiceal Mucinous Neoplasm]

Area of Science:

• Gastroenterology
• Oncology
• Pathology

Background:

• Appendiceal mucinous neoplasms represent a spectrum of epithelial tumors.
• Accurate classification is crucial for appropriate patient management and prognosis.
• High-grade appendiceal mucinous neoplasm (HAMN) is a recently defined entity.

Observation:

• A 70-year-old woman presented with abscess-forming appendicitis, treated conservatively.
• Computed tomography revealed a cystic lesion at the appendiceal base post-treatment.
• Histopathological examination of the resected appendix showed atypical mucinous cells without invasive growth.

Findings:

• The initial diagnosis of low-grade appendiceal mucinous neoplasm (LAMN) was revised to high-grade appendiceal mucinous neoplasm (HAMN).
• HAMN is recognized in the 2019 WHO classification as a distinct category.
• This represents one of the few reported cases of HAMN in Japan.

Implications:

• This case underscores the importance of thorough histopathological evaluation for accurate diagnosis of appendiceal mucinous neoplasms.
• The rarity of HAMN necessitates further research and inclusion in clinical guidelines.
• Accurate classification of HAMN impacts treatment strategies and patient outcomes.