AbstractBackgroundLymph node metastasis (LN+) is a prognostic factor in appendiceal cancers, but predictors and outcomes for LN+ in mucinous appendiceal adenocarcinoma (MAC) remain poorly defined.MethodsPatients were identified from the 2010 to 2016 NCDB who underwent surgical resection as first‐line management for Stage I‐III mucinous appendiceal cancer. A LN+ risk‐score model was developed using multivariable regression on a training data set and internally validated using a testing data set. Three‐year overall survival (OS) was analyzed by Cox proportional hazards regression.ResultsOf 1158 patients, LN+ (N = 244, 21.1%) patients were more likely to have higher pT group and grade of disease, lymphovascular invasion (LVI), and positive margins on univariate analyses. Predictive factors associated with LN+ on multivariable analysis included positive surgical margins (odds ratio [OR] 3.00, P <.0001), higher grade (moderately differentiated: OR, 2.16, P < .0001; poorly or undifferentiated: OR, 3.07, P < .0001), and LVI (OR, 7.28, P < .0001). A validated risk‐score model using these factors was developed with good performance (AUC 0.749). LN+ patients had a worse 3‐year OS compared with LN− patients (17.4% vs 82.6%, hazard ratio 1.96, P = .001).ConclusionsLN+ is associated with worse survival in patients with MAC. A risk‐score model using margin status, LVI, and grade can accurately risk stratify patients for LN+.