eP340 - Extremely Delayed Presentation of Pseudomyxoma Peritonei and Pulmonary Metastasis from Low Grade Appendiceal Mucinous Neoplasm

Purpose/Background: Peritoneal carcinomatosis and pseudomyxoma peritonei (PSP) is common after a ruptured low grade appendiceal mucinous neoplasm (LAMN). The presentation is indolent and may take years to develop. Dissemination of disease is often confined to the peritoneum and leads to development of gelatinous deposits and ascites. Distant spread beyond the abdominal cavity is uncommon but can occur.Methods/Interventions: We describe a rare case of a patient presenting with an extremely long interval from inciting event (perforated appendix) to development of PSP in the setting of biopsy proven LAMN. Additionally, the patient developed biopsy proven pulmonary metastasis 3 years after cytoreductive surgery.Results/Outcomes: A 63-year-old-man with history of appendectomy for ruptured appendicitis 19 years prior, presented to the colorectal surgery clinic with complaints of abdominal pain, bloating, and distention associated with a recent 30-pound unintentional weight loss. Work-up revealed abdominal ascites and imaging findings concerning for peritoneal carcinomatosis. Subsequent CT-guided biopsy of the tumor deposits showed intestinal type glandular epithelium with extensive mucin, highly suspicious for low-grade mucinous neoplasm. The patient subsequently underwent, cytoreductive surgery with hyperthermic intra-peritoneal chemotherapy (HIPEC) followed by early postoperative intraperitoneal chemotherapy (EPIC). The patient’s peritoneal cancer index (PCI) score was 28 at the time of operation, but complete cytoreduction was achieved.

The patient recovered well after surgery and was followed with surveillance imaging every 6 months. He was then found to have abdominal peritoneal recurrence 2 years postoperatively. This was observed with serial imaging and CEA levels without re-operation since he remained asymptomatic, and the peritoneal recurrence did not progress. Then, 3-years postoperatively the patient was found to have a new pulmonary nodule on surveillance imaging. Colonoscopy revealed no new lesions or undiagnosed colorectal malignancy. The pulmonary nodule was followed, but gradually progressed and the patient underwent robotic bronchoscopy with fine needle aspiration and biopsy of the nodule nearly 5 years after cytoreduction.

Review of the pathology confirmed the presence of a mucinous neoplasm with lepidic growth, most consistent with appendiceal origin. The patient has not undergone repeat operation and was most recently seen by medical oncology with plans for systemic chemotherapy.Conclusion/

Discussion: While peritoneal spread and development of PSP is an indolent process, this case is unique in that there was an 18-year interval from the inciting event (perforated appendix) to symptom development. Additionally, the potential for distant metastatic spread from LAMN is an extremely rare occurrence with few cases ever reported. Most cases of pleuropulmonary spread are thought to be via defects within the diaphragm leading to extra-pleural deposits. Intraparenchymal lung metastasis from LAMN is even more rare and the mechanism of spread is still not well understood. This case remains unique due to the extremely long interval from inciting event (ruptured appendix) to development of symptoms, and subsequent development of biopsy proven pulmonary metastasis, more than 22 years later.