Clinicopathological spectrum of appendiceal mucinous neoplasms and associated pseudomyxoma peritonei

Objectives: Appendiceal mucinous neoplasms (AMNs) are uncommon tumors distinguished by dysplastic characteristics and typically manifest with atypical symptoms. These tumors demonstrate varied biological behaviors, and around 40% are initially misdiagnosed as acute appendicitis. Pseudomyxoma peritonei (PMP) is a rare disorder characterized by the buildup of mucinous deposits within the abdominal cavity. It typically begins with mucinous tumors in the appendix that spread gelatinous material to surrounding tissues and organs. The condition may involve cancerous or non-cancerous cells. While PMP has been recognized for many years, there have been recent efforts to create a standardized classification system to guide treatment strategies and clinical management. The aim of this study was to evaluate the clinicopathological spectrum of AMN by analyzing the appendectomy specimens, with specific emphasis on the importance of histopathological examination. Material and Methods: Between 2016 and 2019, a retrospective analysis was performed on a cohort of patients with AMN, comparing outcomes for those with and without PMP. Results: This study examined 13 cases of AMN. The demographic breakdown showed a male-to-female ratio of approximately 1.07:1, with a median age of 53.8 years, ranging from 42 to 70 years. Most patients initially presented with symptoms consistent with acute appendicitis, such as right lower quadrant pain. Among them, 69% had low-grade AMN, while the remaining cases exhibited high-grade features. Peritoneal biopsies were performed in 53% of cases. Of those, 5 out of 7 (71.42%) revealed low-grade mucinous carcinoma peritonei/disseminated peritoneal adenomucinosis (DPAM), 1 out of 7 (14.28%) showed high-grade mucinous carcinoma peritonei/peritoneal mucinous carcinomatosis (PMCA), and 1 out of 7 (14.28%) contained mucin without epithelial cells. Conclusion: Appendiceal neoplasms associated with PMP are infrequent, but the incidence of this condition has been steadily rising. Early detection and intervention are of vital importance due to its unusual appearance and variable biological behavior. A strong collaborative effort between the pathologist, surgeon, and oncologist is essential for a proper and effective histopathologic classification and prediction of tumor behavior. This reimposes the fact that both pathologists and clinicians should update themselves with the latest consensus guidelines as this will enable them to follow uniform terminology and institute a multidisciplinary team approach for appropriate management.