The patient tissue and corresponding organoid models were profiled for protein expression of relevant endometrial cancer markers: ER, PR, L1CAM, PTEN, ARID1A, and assigned to molecular subgroups according to the TCGA-like classification by evaluating IHC staining of P53 and MMR proteins (MSH6, MSH2, PMS2, and MLH1), and by Sanger sequencing of POLE41 (Fig. 2a). Here, MSH2 is linked to endometrial cancer.