ERBB2 and cancer: Variable BC subtypes, luminal, Her2+, and triple-negative can be classified by differential expression of FAP, SMA, FSP1, PDGFRβ, CD29, and CAV1, with the expression of FAP identifying subpopulations that modulate tumor growth, cancer cell proliferation, extracellular matrix remodeling, metastatic dissemination, immunosuppression, and resistance to treatment [220].