A Diagnostic Dilemma: High-Grade Appendiceal Mucinous Neoplasm Presenting as Acute Appendicitis in a 16-Year-Old Female – Case Report and Literature Review

Introduction: High-grade appendiceal mucinous neoplasms (HAMNs) are rare mucin-producing epithelial tumors of the appendix, typically seen in middle-aged to elderly individuals. They are defined by high-grade cytologic atypia and complex architecture but without infiltrative invasion. Occurrence in pediatric or adolescent patients is virtually unknown. Case Presentation: We report a 16-year-old female who presented with signs and symptoms suggestive of acute appendicitis. Ultrasonography supported the diagnosis. A laparoscopic appendectomy was performed. Gross examination revealed a dilated appendix with mucoid contents. Histopathological evaluation confirmed HAMN confined to the appendix. Conclusion: To our knowledge, this is the second reported case of HAMN in an adolescent. This case underscores the importance of histopathologic evaluation of all appendectomy specimens, even in young patients, due to the possibility of underlying neoplasia.