Background: Although WD SI-NETs are typically biologically indolent, they tend to metastasize. PC is a dreaded regional metastatic complication in pts with SI-NETs and contributes to significant morbidity and mortality. Risk factors for PC development in these pts are not well studied, however one factor may be MTD presence. Our analysis is the first to suggest an association between MTD presence and PC in this pt subgroup. Methods: We performed a retrospective analysis on 191 WD SI-NET samples from Vanderbilt University Medical Center with mesenteric masses identified on gross pathology or radiographic review. Of 138 samples with suspected MTDs, 79 were confirmed definitively by detailed pathologic review and 59 were considered likely based on descriptions from surgical pathology reports. We assessed whether pts in our cohort with MTDs had greater rates of PC compared to those without MTDs. We also assessed what other patient determinants were associated with PC and the prognostic role of these determinants. Results: Pts with suspected MTDs had an odds ratio (OR) of 3.9 for PC compared to pts without MTDs. Rates of PC in pts with definitive MTDs and those with likely MTDs were not significantly different (OR 1, p = 1.00). Although suspected MTD presence was not associated with poorer OS (p = 0.97), pts with confirmed MTDs had a trend toward poorer overall survival (OS) than pts with likely MTDs (p = 0.05). PC was a negative prognostic factor in all pts with regards to OS (p = 0.044). Conclusions: SI-NET pts with MTDs appear to have significantly increased rates of PC compared to those without mesenteric deposits. We believe this observation merits prospective evaluation given its potential therapeutic implications. If confirmed prospectively, pts with MTDs could benefit from earlier use of cytoreductive therapies to hinder development of PC.