MMR deficient undifferentiated/dedifferentiated endometrial carcinomas showing significant programmed death ligand-1 expression (sp 142) with potential therapeutic implications.

BACKGROUND

Uterine undifferentiated (UEAC)/dedifferentiated (DEAC) carcinomas are rare malignant neoplasms. They appear to pursue an aggressive clinical course with an advanced stage at presentation. Recently, it was discovered that the use of immunotherapeutic drugs targeting programmed cell death protein 1 (PD1)/programmed death ligand-1 (PD-L1) was associated with improved survival in several types of cancer (especially in patients with mismatch-repair (MMR) deficient patients). Whether these findings can be applied to UEAC/DEAC remains a question. Herein, the aim of this study is to evaluate the expression of PD-L1/PD-1 in UEAC/DEAC and its relationship to MMR status. This could offer useful therapeutic information.

DESIGN

Review of endometrial carcinoma (EC) diagnosed over the period of 2011 to 2017 in our institution identified 14 UEAC/DEAC cases (n=14). All cases had immunohistochemistry performed for MMR (MLH1, PMS2, MSH2 and MSH6), PD-L1 and PD-1. The protein expression was examined and in DEAC cases both the undifferentiated component and the low grade component were recorded separately. The expression of PD-L1 and PD-1 was scored in both the tumor and the peritumoral lymphocyte infiltration.

RESULTS

Overall variable degrees of tumoral or immune stromal PD-L1 staining (from 1% to 5%), was present in 50.0% (7/14) of UC/DEACs. Seven cases (50%) were PD-1 positive (immune stromal). Five cases (35.7%) showed co-expression of PD-1 and PD-L1 (Figure 1). Worth noting is that PD-1 staining was exclusively present in peritumoral immune cells. Following this the 14 cases were further divided into MMR deficient and MMR proficient groups (Table 1). A total of 8 cases had MMR deficiency (57.1%). There was a statistically significant association for PD-L1 positivity in the MMR deficiency group (p=0.05). However there was no statistically significant differences regarding PD-1 positivity between MMR groups.

CONCLUSIONS

PD-L1 and PD-1 were expressed in majority of MMR-deficient UEAC /DEAC cases. PD-L1 was not expressed in MMR-proficient carcinomas. These findings might help support potential immunotherapy trials in MMR-deficient UEAC /DEAC.