TREM1 expression in breast tumors was predominantly associated with the tumor-infiltrating myeloid compartment, and while TREM1 was observed in all breast cancer subtypes, it was expressed to a higher degree in the non-luminal Basal-like and HER2E subtypes, suggesting that yet unknown molecular properties of these tumors may be more conducive to TREM-1 expression and downstream activation. Here, TREM1 is linked to breast cancer.