Using the MMTV-PyMT tumor model, the authors showed infiltration of precancerous lesions and tumors by three different populations with cytotoxic properties, TCRβ+ T cells, TCRδ+ T cells, and TCR- NK1.1+ NKp46+ innate lymphocytes, all of which express GzmB and share a similar transcriptome. Here, NCR1 is linked to neoplasm.