Table 2.

Categorisation of MBCs based on PD-L1 expression in tumour cells and low or high PD-1 expression in TILs

Type	Tumour microenvironment (PD-L1/PD-1 TILs)	Number of cases (n=71)
1	PD-L1 positive, high PD-1*	16 (23%)
2	PD-L1 negative, low PD-1*	22 (31%)
3	PD-L1 positive, low PD-1*	14 (20%)
4	PD-L1 negative, high PD-1*	19 (26%)

*PD-1 categorisation as high or low is done around the median of 22.5.

MBC, metaplastic breast carcinoma; PD-1, programmed cell death 1; PD-L1; programmed death-ligand 1; TIL, tumour infiltrating lymphocyte.