Fig. 1

Proportion in the occurrence of six types of malignant tumors in prefecture-level regions from October 2018 to March 2022. Note: The base map was created using the standard map with the approval number GS(2020)4630 issued by the Ministry of Natural Resources, and the boundary of the map was not modified. To better reflect the spatial variation in the incidence proportion of each tumor type, we used customized classification intervals (cutoffs) for each map in Fig. 1. This approach allows for the clear visualization of intra-type spatial clustering even for tumor types with lower national average proportions (e.g., urinary and endocrine systems). The color scales are therefore not uniform across maps and are optimized for each tumor type’s data distribution. This is a common approach in thematic mapping when the goal is to visualize spatial patterns rather than directly compare magnitudes across different variables.