ABSTRACT Aim This study aimed to evaluate the correlations between programmed death‐ligand 1 ( PD‐L1 ) expression, the mismatch repair system, and p53 status in endometrial cancer, considering tumor stage. Methods A retrospective analysis of clinicopathological and immunohistochemical data was conducted on 254 patients treated at Holy Cross Cancer Centre (Poland). The majority of patients had endometrioid adenocarcinoma (89.8%) and FIGO stage I disease (69.7%). Results Positive PD‐L1 expression (threshold ≥ 1%) was observed in only 3.9% of cases, while mismatch repair system deficiency and aberrant p53 expression were present in 18.1% and 17.3%, respectively. No significant correlations were found between PD‐L1 expression and clinicopathological parameters, repair system status, or p53 ( p = 0.328 and p = 0.359, respectively). However, a significant association ( p = 0.046) was noted between PD‐L1 positivity and the microsatellite‐unstable/hypermutated molecular subtype, with 30% of PD‐L1 positive tumors exhibiting this subtype compared to 10.2% of PD‐L1 negative tumors. Conclusions No molecular marker demonstrated a significant association with recurrence risk ( p > 0.05), in contrast to the FIGO stage, which showed a significant correlation ( p < 0.001). Although PD‐L1 expression was rare, it was significantly associated with microsatellite instability, highlighting the potential of molecular classification to identify candidates for immunotherapy. However, the low frequency of PD‐L1 positivity and the small sample size warrant caution in interpreting these findings, and further research is needed to confirm the clinical relevance of PD‐L1 in endometrial cancer.
Misiek et al. (Mon,) studied this question.