Arai T, et al. - In the present study, researchers described the clinicopathological and molecular characteristics of poorly differentiated adenocarcinoma (PDA) of the stomach. They found that microsatellite instability (MSI)-positive solid-type PDA had unusual clinicopathological features and that MSI with absent MLH1 and PMS2 expression could play a vital part in tumor development. MSI-positive solid-type PDA might originate from differentiated-type adenocarcinoma from the perspective of histogenesis. Findings suggested a significant association of MSI-positive solid-type PDA with older age, female predominance, lower third location, concordant glandular component, and absent MLH1 and PMS2 expression.