Study of PD-L1 Expression with Association of Pathological Factors and Molecular Subtypes in Breast Carcinoma.

 Programmed death ligand 1 (PD-L1), expressed on cancer cells, shows varied results in the prognosis of breast cancer. This study was conducted to study the expression of PD-L1 in breast carcinoma and to correlate it with pathological, molecular classification and prognostic factors.  PD-L1 expression was correlated with tumor size, histopathological grade, necrosis, lymphovascular, perineurial invasion, lymph node metastasis, molecular classification, and survival in breast carcinoma cases.  Fifty cases were included which showed statistically significant difference of PD-L1 with mean age, tumor size, histopathological grade, lymphovascular emboli, and lymph node metastasis (  < 0.05). Estrogen receptor was strongly positive in 46%, progesterone receptor in 42%, and PD-L1 in 6% of cases. No statistically significant difference between pathological tumor-node-metastasis (TNM) staging and PD-L1 expression (  = 0.354) was observed. Receptor operating characteristic curve analysis showed that at the cutoff of PD-L1 greater than 120, specificity was 56.1%, sensitivity 66.7%, negative predictive value 88.5%, and positive predictive value 25% for predicting living status.  PD-L1 is associated with poor prognostic factors including tumor size, histopathological grade, lymphovascular emboli, and lymph node metastasis in breast carcinoma. However, no significant association was observed between PD-L1 and pathological TNM stage or molecular subtypes of breast carcinoma. It is suggested that immunohistochemical reporting of PD-L1 should be standardized so that it is reproducible and reliable for the evaluation of breast carcinoma. Further, larger studies with extended follow-ups are recommended so that the exact role of PD-L1 as a prognostic marker in breast carcinoma could be ascertained.