These 171 genes (or their product proteins) are carefully chosen to contain the genes such as PIK3CA, PTEN, AKT1, TP53, GATA3, CDH1, RB1, MLL3, MAP3K1, and CDKN1B that are well-known to be important for classification of breast cancer subtypes [2]. The gene discussed is PIK3CA; the disease is breast cancer.