To address the challenge of generalization due to organ-specific differences in the prediction of microsatellite instability (MSI-H) across cancers, the study proposes the Conserved Immune Topology (CIT) method. This method uses unsupervised clustering to identify immune-related regions, integrating biological features such as tertiary lymphoid structures, immune responses around tumors, and multi-scale densities of tumor-infiltrating lymphocytes. Information can be extracted from frozen baseline models without annotation or target domain data. In cross-site, cross-cancer evaluations conducted on the CPTAC-COAD and TCGA-STAD cohorts, which include scanner variations and organizational differences, CIT improved the TransMIL AUC for zero-sample cross-cancer migration from 0.6627 to 0.7161, with an absolute gain of 0.0534 (p=0.003), and all three MIL aggregators showed consistent improvement.