Integrated expression profiling of trophoblast cell-surface antigen 2 (TROP2), folate receptor alpha (FRα), and human epidermal growth factor receptor 2 (HER2) in endometrial Cancer across molecular classes, genomic alterations, and histologic subtypes.

OBJECTIVE: Antibody-drug conjugates (ADCs) are expanding treatment options in endometrial carcinoma, but the distribution of actionable surface targets across histologic, molecular, and genomic subgroups remains incompletely defined. METHODS: This single-institution retrospective tissue microarray (TMA) study included 312 endometrial carcinomas: 158 endometrioid and 154 serous tumors. Trophoblast cell-surface antigen 2 (TROP2) was quantified by histochemical score (H-score); human epidermal growth factor receptor 2 (HER2) was assessed using endometrial carcinoma-specific and gastric/DESTINY-PanTumor02 criteria; and folate receptor alpha (FRα) positivity was defined as ≥75% viable tumor cells with ≥2+ membranous staining. Molecular class was assigned using a hierarchical DNA polymerase epsilon (POLE)-mutant, microsatellite instability/mismatch repair-deficient (MSI/MMRd), p53-abnormal, and no specific molecular profile (NSMP) classifier. Tumor mutational burden (TMB) and recurrent genomic alterations were analyzed in relation to biomarker expression. RESULTS: TROP2 was broadly expressed, with median H-scores of 280 in endometrioid and 200 in serous carcinomas. HER2 gastric-score 2+/3+ expression and FRα positivity were enriched in serous versus endometrioid carcinoma (22.5% vs 8.9% and 20.1% vs 4.4%), restricted to FIGO grade 3 tumors, and concentrated in p53-abnormal disease. FRα positivity was absent in POLE-mutant and MSI/MMRd tumors. HER2 2+/3+ expression correlated with erb-b2 receptor tyrosine kinase 2 (ERBB2) alterations, whereas FRα-positive tumors were enriched for TP53 alterations and showed lower frequencies of ARID1A and PTEN alterations. Triple-negative TROP2/HER2/FRα tumors were uncommon (6/308, 1.9%). CONCLUSIONS: TROP2 is broadly expressed in endometrial carcinoma, whereas HER2 and FRα define a more restricted high-grade, serous/serous-like, p53-abnormal compartment, supporting biomarker-informed ADC development.