ERBB2 and breast cancer: It is now known that HER2-positive breast cancer can have high levels of TILs [44], and PD-L1 [45,46] and the presence of TILs at diagnosis is prognostic of outcome: the number of TILs is inversely correlated with the probability of recurrence and positively correlated with overall survival in HER2-positive breast cancer [44,47,48].