To examine whether the prognostic value of FFAR4 expression is different between breast cancer subtypes, patients were classified into Luminal A (n = 75), Luminal B HER2 negative (n = 86), Luminal B HER2 positive (n = 51), HER2 positive non-luminal (n = 41) and Triple negative (n = 54) subtypes based on pathological subtype definitions [24]. Here, ERBB2 is linked to breast cancer.