Consistently, paired analyses revealed that both the frequency of FGFR2-IIIb positivity and the proportion of positive tumor cells were significantly higher in metastatic lesions than in primary tumors (8% vs. 3%; 75% vs. 47%; P < 0.001)158, highlighting pronounced spatial heterogeneity and further supporting spatial variability of isoform expression within the same patient. Here, FGFR2 is linked to neoplasm.