Surgical and oncologic outcomes for liver resections of cystic neuroendocrine tumor liver metastasis

Background: Cystic neuroendocrine tumor liver metastases (NETLM) are rare and dynamics in the liquid compartment often misinterpreted as rapid progression, affecting selection for liver resection candidates. This study retrospectively evaluates surgical and oncologic outcomes in patients with cystic versus solid NETLM from small bowel and pancreatic primaries. Methods: Between 2000 and 2020, 12 patients with cystic NETLM were identified among 464 patients who underwent >90 % tumor cytoreduction debulking hepatectomy at the Mayo Clinic. Tumor and patient characteristics, as well as surgical and oncologic outcomes, were compared with the total cohort of patients with solid NETLM, including a propensity-matched cohort. Results: Patients with cystic NETLM were similar in age (55.4 vs. 59.7 years; p = 0.113) and sex (58 % vs. 51 % men; p = 0.772) to those with solid NETLM. Synchronous metastases (92 % vs. 77 %; p = 0.314), bilobar distribution (83 % vs. 79 %; p = 1.000), lesion numbers (p = 0.547), Ki67 % expression (p = 0.311), and extrahepatic lesions (8 % vs. 18 %; p = 0.702) were similar. Cystic metastases were larger (7.3 vs. 3.8 cm; p < 0.001). Surgical risk did not differ, with major morbidity (25 % vs. 22 %; p = 0.729) and mortality (0 % vs. <2 %; p = 1.000). Median overall survival (OS) was 13.8 vs. 10.6 years (p = 0.513), and hepatic-progression-free survival (PFS) was 0.71 vs. 1.78 years (p = 0.507). Matched cohorts showed no significant difference in OS (13.80 vs. 8.57; p = 0.316) or hepatic-PFS (0.71 vs. 1.33; p = 0.620). Conclusion: Surgical risk and long-term outcomes do not significantly differ between cystic and solid NETLMs. Given excellent long-term survival rates with >90 % cytoreduction, radical debulking is advised for both phenotypes when clinically feasible.