RAB31 and neoplasm: Recently, Class 1 tumours have been subdivided into two subgroups, Class 1A (2% of patients 5‐year metastatic risk) and Class 1B (21% of patients 5‐year metastatic risk) 125, based on the differential expression of CDH1 and RAB31. Class 1A tumours are also associated with D3 and EIF1AX mutations.