Diagnostic pitfalls in low grade appendiceal mucinous neoplasms

Primary neoplasms of the appendix are present in less than 2% of appendicectomy specimens. Appendiceal mucinous neoplasm is a rare malignancy which is found in less than 0.3% of appendicectomy specimens and accounts for around 1% of gastrointestinal neoplasms. These have varying malignant potential and include a heterogeneous group of diseases. According to the WHO 5th edition (2019), the neoplastic spectrum of appendiceal mucinous neoplasms comprise of low-grade appendiceal mucinous neoplasms (LAMNs), high grade appendiceal mucinous neoplasms (HAMNs), and mucinous adenocarcinoma of the appendix. The patients with mucinous appendiceal lesions are frequently operated for symptoms resembling acute appendicitis as they lack specific clinical and imaging presentation. Categorisation of these neoplasms with attention to extent of mucin and neoplastic cells is crucial to stage the disease as well as to assess the risk of pseudomyxoma peritonei (PMP), a life threatening complication with poor prognosis. We present 8 LAMNs including a rare case of synchronous mucinous cystadenoma of ovary and LAMNs. We discuss the different clinical presentations and the challenges faced in diagnosis.